Check if loop exists for continue

Otherwise the variable might not be defined and
lead to a PHP notice.

Author: iquito

src/TokenParser/ContinueNode.php

@@ -23,6 +23,8 @@ public function compile(Compiler $compiler)
     {
         $compiler
             ->addDebugInfo($this)
+            ->write("if (isset(\$context['loop'])) {\n")
+            ->indent()
             // Taken from ForLoopNode - need to do this otherwise the continue skips it
             ->write("++\$context['loop']['index0'];\n")
             ->write("++\$context['loop']['index'];\n")
@@ -34,6 +36,9 @@ public function compile(Compiler $compiler)
             ->write("\$context['loop']['last'] = 0 === \$context['loop']['revindex0'];\n")
             ->outdent()
             ->write("}\n")
+            // End taken from FoorLoopNode
+            ->outdent()
+            ->write("}\n")
             // Do the actual continue operation
             ->write("continue " . $this->loopNumber . ";\n")
         ;