Describe the bug
When the source code file is larger than 10K lines the .gcov format appears to drop the space between %%%%%: and the line number. This causes _RE_BLOCK_LINE to not match since it requires the space to be present.

Slightly redacted .gcov extract:

    %%%%%: 9998-block  1
call    6 never executed
    #####: 9999:    child_->set_access([...]);
call    0 never executed
branch  1 never executed (fallthrough)
branch  2 never executed (throw)
    #####:10000:    setReadAccess(*child_);
    %%%%%:10000-block  0
call    0 never executed
branch  1 never executed (fallthrough)
branch  2 never executed (throw)
    #####:10001:    child_ = child_->add_child([...]);
    %%%%%:10001-block  0

To Reproduce
Steps to reproduce the behavior:

1. Generate coverage data for a file with at least 10000 lines of code
2. gcovr -r . --html-details -o coverage/index.html (or similar)
3. gcovr dumps all -block lines with line number 10000 or higher, then fails with gcovr.formats.gcov.parser.UnknownLineType: %%%%%:10000-block 0

Expected behavior
_RE_BLOCK_LINE should matches lines 10000 and later

Desktop (please complete the following information):

• OS: Debian testing
• GCC version: Debian 13.2.0-13
• GCOVR version 7.0

Additional context
When I deleted the .gcno file for the large .cpp file the report for the other files was generated successfully