[fix] wikipedia: minor fix: return no result instead of crash in some very few cases.

In few cases, the JSON results doesn't contains the key 'type'.

searx/engines/wikipedia.py

@@ -52,7 +52,7 @@ def response(resp):
     api_result = loads(resp.text)
 
     # skip disambiguation pages
-    if api_result['type'] != 'standard':
+    if api_result.get('type') != 'standard':
         return []
 
     title = api_result['title']