fix: prevent empty selector error in SurveyLoadingAnimation

- Add type guard for isWelcomeCardEnabled to ensure it's a boolean
- Add validation before querySelectorAll to prevent empty selector errors
- Add guard in checkMediaLoaded callback for defensive programming

Fixes FORMBRICKS-K3

apps/web/modules/survey/link/components/survey-loading-animation.tsx

@@ -20,10 +20,20 @@ export const SurveyLoadingAnimation = ({
   const [isMediaLoaded, setIsMediaLoaded] = useState(false); // Tracks if all media are fully loaded
   const [isSurveyPackageLoaded, setIsSurveyPackageLoaded] = useState(false); // Tracks if the survey package has been loaded into the DOM
   const isReadyToTransition = isMediaLoaded && minTimePassed && isBackgroundLoaded;
-  const cardId = isWelcomeCardEnabled ? `questionCard--1` : `questionCard-0`;
+  // Ensure cardId is always a valid string by explicitly checking for boolean type
+  const cardId =
+    typeof isWelcomeCardEnabled === "boolean" && isWelcomeCardEnabled
+      ? `questionCard--1`
+      : `questionCard-0`;
 
   // Function to check if all media elements (images and iframes) within the survey card are loaded
   const checkMediaLoaded = useCallback(() => {
+    // Guard against empty cardId
+    if (!cardId) {
+      setIsMediaLoaded(true);
+      return;
+    }
+
     const cardElement = document.getElementById(cardId);
     const images = cardElement ? Array.from(cardElement.getElementsByTagName("img")) : [];
 
@@ -37,6 +47,12 @@ export const SurveyLoadingAnimation = ({
   useEffect(() => {
     if (!isSurveyPackageLoaded) return;
 
+    // Guard against empty cardId to prevent "'' is not a valid selector" error
+    if (!cardId) {
+      setIsMediaLoaded(true);
+      return;
+    }
+
     checkMediaLoaded();
 
     const mediaElements = document.querySelectorAll(`#${cardId} img, #${cardId} iframe`);