Fix NPE in PipTaskOrganizer#setPipVisible

Bug: 286873981
Test: N/A, fix NPE as it is
Change-Id: Iae33e2d1a91603f264632e85e6fcbaaec576a7e2

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTaskOrganizer.java

@@ -1146,7 +1146,7 @@ public class PipTaskOrganizer implements ShellTaskOrganizer.TaskListener,
     public void setPipVisibility(boolean visible) {
         ProtoLog.d(ShellProtoLogGroup.WM_SHELL_PICTURE_IN_PICTURE,
                 "setPipVisibility: %s, state=%s visible=%s",
-                mTaskInfo.topActivity, mPipTransitionState, visible);
+                (mTaskInfo != null ? mTaskInfo.topActivity : null), mPipTransitionState, visible);
         if (!isInPip()) {
             return;
         }