Fix issue with global fallback when not in global space

Zend/tests/use_function/no_global_fallback2.phpt

@@ -0,0 +1,18 @@
+--TEST--
+non-existent imported functions should not be looked up in the global table
+--FILE--
+<?php
+
+namespace {
+	function test() {
+		echo "NO!";
+	}
+}
+namespace foo {
+	use function bar\test;
+	test();
+}
+
+?>
+--EXPECTF--
+Fatal error: Call to undefined function bar\test() in %s on line %d