fix ._hocr

[BBC-Esq]

Fix AttributeError in HocrTransform._get_text_direction when par is None

When processing certain HOCR files, the _get_text_direction method can receive a None value for its par parameter. This occurs when either:

1. The HOCR file lacks properly structured paragraph elements (<p class='ocr_par'>)
2. The fallback case is triggered but self.hocr.find(...) returns None

Without a check for this condition, the method attempts to access par.attrib on a None object, resulting in an AttributeError:

AttributeError: 'NoneType' object has no attribute 'attrib'

The Fix

This PR adds a simple null check to handle the case where par is None, returning the default left-to-right text direction instead of crashing.

This change:

• Prevents crashes when processing HOCR files with missing or malformed paragraph structures
• Maintains backward compatibility (same return values and behavior for valid inputs)
• Simplifies error handling for clients of this library
• Follows the principle of defensive programming

Example File - error occurring when processing Page 115

DivXGuide51.pdf

[BBC-Esq]

Please note that this fix isn't perfect. For RTL langauges, for example, you might do a subsequent PR like this:

def _get_text_direction(self, par):
    """Get the text direction of the paragraph.

    Arabic, Hebrew, Persian, are right-to-left languages.
    
    When the paragraph element is None, attempts to infer direction from
    other paragraphs in the document, defaulting to left-to-right.
    """
    if par is None:
        # Try to infer from other paragraphs in the document
        for p in self.hocr.iterfind(self._child_xpath('p', 'ocr_par')):
            if p is not None and p.attrib.get('dir') == 'rtl':
                return TextDirection.RTL
        return TextDirection.LTR
        
    return (
        TextDirection.RTL
        if par.attrib.get('dir', 'ltr') == 'rtl'
        else TextDirection.LTR
    )

However, this PR should resolve a vast majority of the issues.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.11%. Comparing base (7b2dd89) to head (0970ceb).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ocrmypdf/hocrtransform/_hocr.py	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1493      +/-   ##
==========================================
- Coverage   90.14%   90.11%   -0.03%     
==========================================
  Files          95       95              
  Lines        7133     7135       +2     
  Branches      728      729       +1     
==========================================
  Hits         6430     6430              
- Misses        497      498       +1     
- Partials      206      207       +1     

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[BBC-Esq]

Anyone going to review this?