Merge pull request #208 from Unity-Technologies/zgh/fix_renderMode

fix: renderMode error

com.unity.uiwidgets/Runtime/engine/UIWidgetsPanel.cs

         }
 
         Vector2? _getPointerPosition(Vector2 position) {
-            var worldCamera = canvas.worldCamera;
+            var worldCamera = canvas.renderMode == RenderMode.ScreenSpaceOverlay ? null : canvas.worldCamera;
             if (RectTransformUtility.ScreenPointToLocalPointInRectangle(
                 rect: rectTransform, screenPoint: position, cam: worldCamera, out var localPoint)) {
                 var scaleFactor = canvas.scaleFactor;