fix(core utils): jqToNode: Don't break when nothing was passed.

Author: thet

src/core/utils.js

@@ -618,7 +618,7 @@ const isIE = () => {
 
 const jqToNode = (el) => {
     // Return a DOM node if a jQuery node was passed.
-    if (el.jquery) {
+    if (el?.jquery) {
         el = el[0];
     }
     return el;

src/core/utils.test.js

@@ -650,6 +650,13 @@ describe("core.utils tests", () => {
 
             done();
         });
+
+        it("it returns the empty value, if no element was passed.", (done) => {
+            expect(utils.jqToNode(null)).toBe(null);
+            expect(utils.jqToNode(undefined)).toBe(undefined);
+
+            done();
+        });
     });
 
     describe("ensureArray tests", () => {