Add defensive code around Cluster.broadcastConnectUpdate (#5297)

src/common/cluster/cluster.ts

@@ -504,7 +504,9 @@ export class Cluster implements ClusterModel, ClusterState {
           return ClusterStatus.AccessDenied;
         }
 
-        this.broadcastConnectUpdate(error.error || error.message, true);
+        const message = String(error.error || error.message) || String(error);
+
+        this.broadcastConnectUpdate(message, true);
 
         return ClusterStatus.Offline;
       }
@@ -521,7 +523,9 @@ export class Cluster implements ClusterModel, ClusterState {
         return ClusterStatus.AccessDenied;
       }
 
-      this.broadcastConnectUpdate(error.message, true);
+      const message = String(error.error || error.message) || String(error);
+
+      this.broadcastConnectUpdate(message, true);
 
       return ClusterStatus.Offline;
     }

src/common/utils/type-narrowing.ts

@@ -73,6 +73,14 @@ export function isString(val: unknown): val is string {
   return typeof val === "string";
 }
 
+/**
+ * checks if val is of type boolean
+ * @param val the value to be checked
+ */
+export function isBoolean(val: unknown): val is boolean {
+  return typeof val === "boolean";
+}
+
 /**
  * checks if val is of type object and isn't null
  * @param val the value to be checked