from typing import Optional

def fix_invalid_syntax_error(error_message: str) -> Optional[str]:
    """
    Attempts to fix an invalid syntax error by removing the offending line.

    Args:
        error_message (str): The error message containing the invalid syntax error.

    Returns:
        Optional[str]: The modified code with the offending line removed, or None if the error message
        does not contain a valid line number and code snippet.
    """
    # Check if the error message follows the expected format
    if "Code snippet near error:" in error_message:
        lines = error_message.split("\n")
        for i, line in enumerate(lines):
            if line.startswith("Code snippet near error:"):
                code_line_number = int(lines[i - 1].split(":")[0])
                code_snippet = "\n".join(lines[i + 1:])
                code_lines = code_snippet.split("\n")
                if code_line_number <= len(code_lines):
                    modified_code = "\n".join(code_lines[:code_line_number - 1] + code_lines[code_line_number:])
                    return modified_code
    return None