FE: Disable resetting offsets for unassigned CGs (#3935)

kafka-ui-react-app/src/components/ConsumerGroups/Details/Details.tsx

@@ -54,6 +54,8 @@ const Details: React.FC = () => {
     ? filteredPartitionsByTopic
     : Object.keys(partitionsByTopic);
 
+  const hasAssignedTopics = consumerGroup?.data?.topics !== 0;
+
   return (
     <div>
       <div>
@@ -71,6 +73,7 @@ const Details: React.FC = () => {
                   action: Action.RESET_OFFSETS,
                   value: consumerGroupID,
                 }}
+                disabled={!hasAssignedTopics}
               >
                 Reset offset
               </ActionDropdownItem>

kafka-ui-react-app/src/components/ConsumerGroups/Details/ResetOffsets/ResetOffsets.tsx

@@ -21,7 +21,7 @@ const ResetOffsets: React.FC = () => {
     return <PageLoader />;
 
   const partitions = consumerGroup.data.partitions || [];
-  const { topic } = partitions[0];
+  const { topic } = partitions[0] || '';
 
   const uniqTopics = Array.from(
     new Set(partitions.map((partition) => partition.topic))