Check if `mDragResizeListener` is null before use in `DesktopModeWindowDecoration`

Prevents null pointer exception being thrown leading to sysui crash.

Fixes: 332874241
Test: manual
Change-Id: I883526d7077c9e37761ace8b9e68452e9d33acb9
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/DesktopModeWindowDecoration.java b/libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/DesktopModeWindowDecoration.java
index f790d2a..d0879434 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/DesktopModeWindowDecoration.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/DesktopModeWindowDecoration.java
@@ -425,7 +425,7 @@
     }
 
     boolean shouldResizeListenerHandleEvent(MotionEvent e, Point offset) {
-        return mDragResizeListener.shouldHandleEvent(e, offset);
+        return mDragResizeListener != null && mDragResizeListener.shouldHandleEvent(e, offset);
     }
 
     boolean isHandlingDragResize() {
@@ -795,7 +795,7 @@
      */
     private Region getGlobalExclusionRegion() {
         Region exclusionRegion;
-        if (mTaskInfo.isResizeable) {
+        if (mDragResizeListener != null && mTaskInfo.isResizeable) {
             exclusionRegion = mDragResizeListener.getCornersRegion();
         } else {
             exclusionRegion = new Region();