Use isset() over strlen() for better performance

Author: fredden

src/Standards/Squiz/Sniffs/Commenting/FunctionCommentSniff.php

@@ -406,7 +406,7 @@ protected function processParams(File $phpcsFile, $stackPtr, $commentStart)
 
             foreach ($typeNames as $typeName) {
                 // Strip nullable operator.
-                if (strlen($typeName) > 1 && $typeName[0] === '?') {
+                if (isset($typeName[0]) === true && $typeName[0] === '?') {
                     $typeName = substr($typeName, 1);
                 }