[fix] command engine: SearchQuery.query is str not bytes

see c225db45c8a4ab466bff049216f7e0189dc1b067

searx/engines/command.py

@@ -80,7 +80,7 @@ def search(query, params):
 
 
 def _get_command_to_run(query):
-    params = shlex_split(query.decode('utf-8'))
+    params = shlex_split(query)
     __check_query_params(params)
 
     cmd = []