fix: handle missing semicolon in abstract function declarations

[dmzoneill]

Summary

• Prevents crash when processing malformed abstract/interface function declarations
• Adds early return when semicolon is not found
• Allows syntax errors to be reported by appropriate sniffs

Problem

When linting PHP code with malformed abstract/interface methods (missing both semicolon and curly braces), the FunctionDeclarationSniff crashes with:

Undefined array key -1 in FunctionDeclarationSniff.php on line 130

Example malformed code:

<?php
public function process(Schema $schema, string $query, array $context, array $vars, callable $next)

The crash occurs because:

1. Line 129 calls findNext(T_SEMICOLON, $closeBracket) which returns false when no semicolon exists
2. Line 130 attempts to access $tokens[($end - 1)] where $end = false
3. This evaluates to $tokens[-1], causing the undefined array key error

Solution

Added a check after findNext() to detect when no semicolon is found:

• If $end === false, the function returns early
• This prevents the undefined array access
• Other sniffs can properly report the actual syntax error in the PHP code

Testing

Tested with the reproduction case from the issue:

• Before: Fatal error with "Undefined array key -1"
• After: Graceful handling, allowing proper error reporting

Fixes #3917

[jrfnl]

Didn't I tell you this already today ?

Please don't open issues in this repo. This repo is abandoned and https://github.com/PHPCSStandards/PHP_CodeSniffer is its successor. See: #3932

P.S.: and don't use AI.