Fix phpcbf crash in UnnecessaryNamespaceUsageSniff when class name is emptry, fixes mayflower#212

Author: xalopp

MO4/Sniffs/Formatting/UnnecessaryNamespaceUsageSniff.php

@@ -230,7 +230,12 @@ protected function getUseStatements(File $phpcsFile, int $start, int $end): arra
                 $end,
                 true
             );
-            $useEnd         = $phpcsFile->findNext(
+
+            if (0 === $classNameEnd) {
+                break;
+            }
+
+            $useEnd = $phpcsFile->findNext(
                 [
                     T_SEMICOLON,
                     T_COMMA,