Fix for key error when sending broadcast trx

Fix for:
{"exception":"KeyError(0,)","message":"Internal Error","error_id":"65c8a0e4-ecd4-4424-a490-7f87cb0c889a","jrpc_request_id":1,"jussi_request_id":"001113248166147000","event":"Internal Error","logger":"jussi.errors","level":"error"}

while sending:
curl -s --data '{"jsonrpc":"2.0", "method":"network_broadcast_api.broadcast_transaction", "params":{"trx":{"ref_block_num":1097,"ref_block_prefix":2181793527,"expiration":"2016-03-24T18:00:21","operations":[{"type":"vote_operation","value":{"voter":"hiveio","author":"alice","permlink":"a-post-by-alice","weight":10000}}],"extensions":[],"signatures":[]},"max_block_age":50}, "id":1}' https://beta.openhive.network

jussi/validators.py

@@ -184,7 +184,7 @@ def limit_broadcast_transaction_request(request: JSONRPCRequest, limits=None) ->
         else:
             raise ValueError(
                 f'Unknown request params type: {type(request.urn.params)} urn:{request.urn}')
-        ops = [op for op in request_params['operations'] if op[0] == 'custom_json']
+        ops = [op for op in request_params['operations'] if op['type'] == 'custom_json']
         if not ops:
             return
         blacklist_accounts = set()