[enh] handle engine response crashes

searx/search.py

     if response:
         # parse the response
         response.search_params = request_params
-        search_results = engine.response(response)
+        try:
+            search_results = engine.response(response)
+        except:
+            logger.exception('engine crash: {0}'.format(engine.name))
+            search_results = []
 
         # add results
         for result in search_results:
         engine.stats['engine_time'] += time() - request_params['started']
         engine.stats['engine_time_count'] += 1
 
-    #
     return success