Generic/ConstructorName: fix minor bug

This commit fixes a minor bug in `Generic.NamingConventions
.ConstructorName` when checking if a given class has a parent. The code
was checking if the lower case version of the value returned by
`File::findExtendedClassName()`` is `false`. The problem is that
`strtolower()` never returns `false`, it always returns a `string`.
Thus, the condition would never evaluate to `true` and the sniff would
not bail at this point when a given class has no parent.

This did not cause any issues to the sniff, even for invalid code, as
there is not a scenario where a class method can have a `T_DOUBLE_COLON`
token followed by a `T_STRING` token with an empty `content`. This is
true even for empty strings as PHPCS includes the quotes in the
`content`.

Author: rodrigoprimo

src/Standards/Generic/Sniffs/NamingConventions/ConstructorNameSniff.php

@@ -94,16 +94,18 @@ protected function processTokenWithinScope(File $phpcsFile, $stackPtr, $currScop
             return;
         }
 
-        $parentClassName = strtolower($phpcsFile->findExtendedClassName($currScope));
+        $parentClassName = $phpcsFile->findExtendedClassName($currScope);
         if ($parentClassName === false) {
             return;
         }
 
+        $parentClassNameLc = strtolower($parentClassName);
+
         $endFunctionIndex = $tokens[$stackPtr]['scope_closer'];
         $startIndex       = $stackPtr;
         while (($doubleColonIndex = $phpcsFile->findNext(T_DOUBLE_COLON, $startIndex, $endFunctionIndex)) !== false) {
             if ($tokens[($doubleColonIndex + 1)]['code'] === T_STRING
-                && strtolower($tokens[($doubleColonIndex + 1)]['content']) === $parentClassName
+                && strtolower($tokens[($doubleColonIndex + 1)]['content']) === $parentClassNameLc
             ) {
                 $error = 'PHP4 style calls to parent constructors are not allowed; use "parent::__construct()" instead';
                 $phpcsFile->addError($error, ($doubleColonIndex + 1), 'OldStyleCall');