Fix ConcurrentModificationException in MultiConnectionKeeper

[DaVinci9196]

06-10 11:38:00.115 E/AndroidRuntime(28150): FATAL EXCEPTION: main
06-10 11:38:00.115 E/AndroidRuntime(28150): Process: com.google.android.gms, PID: 28150
06-10 11:38:00.115 E/AndroidRuntime(28150): java.util.ConcurrentModificationException
06-10 11:38:00.115 E/AndroidRuntime(28150): at java.util.HashMap$HashIterator.nextNode(HashMap.java:1454)
06-10 11:38:00.115 E/AndroidRuntime(28150): at java.util.HashMap$KeyIterator.next(HashMap.java:1478)
06-10 11:38:00.115 E/AndroidRuntime(28150): at org.microg.gms.common.MultiConnectionKeeper$Connection$1.onServiceConnected(MultiConnectionKeeper.java:216)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:2340)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:2373)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.os.Handler.handleCallback(Handler.java:966)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.os.Handler.dispatchMessage(Handler.java:110)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.os.Looper.loopOnce(Looper.java:205)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.os.Looper.loop(Looper.java:293)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.app.ActivityThread.processInnerLoop(ActivityThread.java:10272)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.app.ActivityThread.loopProcess(ActivityThread.java:10264)
06-10 11:38:00.115 E/AndroidRuntime(28150): at android.app.ActivityThread.main(ActivityThread.java:10255)
06-10 11:38:00.115 E/AndroidRuntime(28150): at java.lang.reflect.Method.invoke(Native Method)
06-10 11:38:00.115 E/AndroidRuntime(28150): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
06-10 11:38:00.115 E/AndroidRuntime(28150): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1366)

[sysxda]

getting simiral error

06-07 16:35:22.191  4328  4328 D AndroidRuntime: Shutting down VM
06-07 16:35:22.194  4328  4328 E AndroidRuntime: FATAL EXCEPTION: main
06-07 16:35:22.194  4328  4328 E AndroidRuntime: Process: com.google.android.gms, PID: 4328
06-07 16:35:22.194  4328  4328 E AndroidRuntime: java.util.ConcurrentModificationException
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1603)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at java.util.HashMap$ValueIterator.next(HashMap.java:1631)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at org.microg.gms.auth.phone.SmsRetrieverCore.onDestroy(SmsRetrieverCore.kt:237)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.DefaultLifecycleObserverAdapter.onStateChanged(DefaultLifecycleObserverAdapter.kt:29)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.kt:322)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.LifecycleRegistry.backwardPass(LifecycleRegistry.kt:273)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.kt:290)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.kt:143)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.kt:126)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at androidx.lifecycle.ServiceLifecycleDispatcher$DispatchRunnable.run(ServiceLifecycleDispatcher.kt:92)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.os.Handler.handleCallback(Handler.java:1070)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:125)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.os.Looper.dispatchMessage(Looper.java:333)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.os.Looper.loopOnce(Looper.java:263)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:367)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:9345)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:569)
06-07 16:35:22.194  4328  4328 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:837)

[peterhel]

Nice catch — real bug, and the fix is correct. Ran a quick 5-whys to make sure it hits root, not just symptom:

1. Why the crash? ConcurrentModificationException thrown while iterating connectionForwards in the serviceConnection callback.
2. Why the CME? The HashSet was structurally modified mid-iteration from another thread.
3. Why concurrent modification? The callbacks (onServiceConnected/onServiceDisconnected, ~lines 216/228) iterate on the main thread off-lock, while add/removeConnectionForward mutate the set under the synchronized bind/unbind path — read and write don't share a lock.
4. Why no shared lock? The async ServiceConnection callbacks were never brought under the keeper's synchronization, nor was the set made thread-safe — the class assumed single-threaded access that the async-callback model breaks.
5. Why missed? (root) Connection straddles two concurrency domains — caller-driven mutation (synchronized) and framework-driven async callbacks (unsynchronized) — over shared mutable state, with no single explicit thread-safety policy for it.

This PR closes #1–#3 cleanly and hardens the shared fields with the concurrent set + volatile — the crash is gone, and it's the right scoped fix. The only root-level leftover is #5: a couple of compound check-then-act sequences (e.g. addConnectionForward does add(...) then if (connected) → onServiceConnected(...)) are still technically racy against the async callback that flips connected and iterates, so a forward could in theory double- or miss a callback. Latent, rare, and clearly out of scope here — just flagging for a possible follow-up.

Builds cleanly in-tree for me. LGTM 👍

(Tiny nit, take it or leave it: stray double space in connectionForwards = Collections....)