fixed typo

src/Parser.php

@@ -335,7 +335,7 @@ class Parser implements \Twig_ParserInterface
     public function getImportedSymbol($type, $alias)
     {
         if (null !== $this->peekBlockStack()) {
-            foreach ($this->importedSymbols as $i => $functions) {
+            foreach ($this->importedSymbols as $functions) {
                 if (isset($functions[$type][$alias])) {
                     if (count($this->blockStack) > 1) {
                         return null;