fix: don't crash linting on compile errors without line info (#3358)

[xiangnuans]

Problem

lint_python_compile (in aider/linter.py) assumed every compile error carries lineno / end_lineno. Two real cases break that assumption and crash linting for the whole file — reported as "Uncaught TypeError in linter.py" in #3358 (and the dup #3378, "source code string cannot contain null bytes"):

• A source string containing null bytes raises ValueError with no lineno attribute at all, so getattr(err, "end_lineno", err.lineno) itself raised AttributeError.
• Some SyntaxErrors carry lineno=None, so err.lineno - 1 raised TypeError: unsupported operand type(s) for -: 'NoneType' and 'int'.

Confirmed on current main (Python 3.13): compile("x=1\0y=2", ...) raises a SyntaxError with lineno=None, and the existing code crashes with exactly that TypeError.

Fix

Read the line info defensively and fall back to an empty line list when it's missing/None, so the compile error is still surfaced to the user instead of taking down linting:

lineno = getattr(err, "lineno", None)
if lineno is None:
    line_numbers = []
else:
    end_lineno = getattr(err, "end_lineno", None) or lineno
    line_numbers = list(range(lineno - 1, end_lineno))

Tests

Added regression tests in tests/basic/test_linter.py:

• null bytes no longer crash
• SyntaxError with lineno=None no longer crashes
• normal syntax error still reports its line (happy-path guard)
• valid code still returns None

pytest tests/basic/test_linter.py → 10 passed, 1 skipped (Windows-only).

Fixes #3358

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