[enh] allow default empty values for normal and result proxies

searx/poolrequests.py

 def request(method, url, **kwargs):
     """same as requests/requests/api.py request(...) except it use SessionSinglePool and force proxies"""
     session = SessionSinglePool()
-    kwargs['proxies'] = settings['outgoing'].get('proxies', None)
+    kwargs['proxies'] = settings['outgoing'].get('proxies') or None
     response = session.request(method=method, url=url, **kwargs)
     session.close()
     return response

searx/webapp.py

                    gettext('map'),
                    gettext('science'))
 
-outgoing_proxies = settings['outgoing'].get('proxies', None)
+outgoing_proxies = settings['outgoing'].get('proxies') or None
 
 
 @babel.localeselector
 
     kwargs['image_proxify'] = image_proxify
 
-    kwargs['proxify'] = proxify if settings.get('result_proxy') else None
+    kwargs['proxify'] = proxify if settings.get('result_proxy', {}).get('url') else None
 
     kwargs['get_result_template'] = get_result_template