[fix] duckduckgo engine: logger.error / missing argument (#5057)

The error message in case the vqd value could not be determined was incorrect
and triggered an exception::

     File "/usr/local/searxng/searxng-src/searx/engines/duckduckgo.py", line 132, in get_vqd
       logger.error("vqd value from duckduckgo.com ", resp.status_code)
     Message: 'vqd value from duckduckgo.com '
     Arguments: (202,)

searx/engines/duckduckgo.py

@@ -129,7 +129,7 @@ def get_vqd(query: str, region: str, force_request: bool = False) -> str:
     if value:
         cache.set(key=key, value=value)
     else:
-        logger.error("vqd value from duckduckgo.com ", resp.status_code)
+        logger.error("none vqd value from duckduckgo.com: HTTP %s", resp.status_code)
     return value
 
 

searx/results.py

@@ -88,10 +88,12 @@ class ResultContainer:
             if isinstance(result, Result):
                 result.engine = result.engine or engine_name
                 result.normalize_result_fields()
+                if not self.on_result(result):
+                    continue
 
-                if isinstance(result, BaseAnswer) and self.on_result(result):
+                if isinstance(result, BaseAnswer):
                     self.answers.add(result)
-                elif isinstance(result, MainResult) and self.on_result(result):
+                elif isinstance(result, MainResult):
                     main_count += 1
                     self._merge_main_result(result, main_count)
                 else: