Only show message to stop instance when instance has been selected (#2962)

* Update logic for message display re: stopping the instance

* Article update: *This* instance …

Author: charliepark

app/forms/anti-affinity-group-member-add.tsx

@@ -77,10 +77,10 @@ export default function AddAntiAffinityGroupMemberForm({ instances, onDismiss }:
               control={form.control}
             />
           </form>
-          {!canAddInstance && (
+          {selectedInstance && !canAddInstance && (
             <Message
               variant="notice"
-              content="An instance must be stopped to add it to a group"
+              content="This instance must be stopped to add it to a group"
             />
           )}
         </Modal.Section>
@@ -89,7 +89,7 @@ export default function AddAntiAffinityGroupMemberForm({ instances, onDismiss }:
         onDismiss={onDismiss}
         actionText="Add to group"
         formId={formId}
-        disabled={!canAddInstance}
+        disabled={!selectedInstance || !canAddInstance}
       />
     </Modal>
   )