Add a warning for dismissing invalid toasts

src/stores/ToastStore.ts

@@ -68,6 +68,11 @@ export default class ToastStore extends EventEmitter {
     }
 
     dismissToast(key) {
+        if (!this.toasts.some(t => t.key === key)) {
+            console.warn(`No toast for ${key} found - cannot dismiss. Check your toastKey`);
+            return;
+        }
+
         if (this.toasts[0] && this.toasts[0].key === key) {
             this.countSeen++;
         }