Add defensive code around Cluster.broadcastConnectUpdate (#5297)

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