Fixed bug that caused "for item in seq if expr" to fail if the loop is not accessing loop

--HG--
branch : trunk
diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index e3b9e53..8b4abf6 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -813,7 +813,7 @@
         # tests in not extended loops become a continue
         if not extended_loop and node.test is not None:
             self.indent()
-            self.writeline('if ')
+            self.writeline('if not ')
             self.visit(node.test, loop_frame)
             self.write(':')
             self.indent()