Fix reference to TouchEvent which is not defined in Firefox

Author: kiasyn

packages/uui-base/lib/utils/drag.ts

@@ -22,11 +22,15 @@ export const drag = (
     const offsetY = dims.top + defaultView.scrollY;
 
     let pointerEvent: PointerEvent | Touch;
-    if (event instanceof TouchEvent) {
+    // TouchEvent is not available in Firefox
+    if ('TouchEvent' in window && event instanceof TouchEvent) {
       pointerEvent = event.touches[0];
-    } else {
+    } else if ( event instanceof PointerEvent ) {
       pointerEvent = event;
     }
+    else {
+      return;
+    }
 
     const x = pointerEvent.pageX - offsetX;
     const y = pointerEvent.pageY - offsetY;