Validate queueableFns

src/core/QueueRunner.js

@@ -37,6 +37,17 @@ getJasmineRequireObj().QueueRunner = function(j$) {
   function QueueRunner(attrs) {
     this.id_ = nextid++;
     this.queueableFns = attrs.queueableFns || [];
+
+    for (const f of this.queueableFns) {
+      if (!f) {
+        throw new Error('Received a falsy queueableFn');
+      }
+
+      if (!f.fn) {
+        throw new Error('Received a queueableFn with no fn');
+      }
+    }
+
     this.onComplete = attrs.onComplete || emptyFn;
     this.clearStack =
       attrs.clearStack ||