Use more strict check for options

Author: vitalk

pytest_flask/plugin.py

@@ -108,7 +108,7 @@ def test_something(app):
 
     app = request.getfuncargvalue('app')
     options = request.keywords.get('options')
-    if options:
+    if options is not None:
         for key, value in options.kwargs.items():
             monkeypatch.setitem(app.config, key.upper(), value)