Validate content overlay before removal

Bug: 234158920
Test: atest --iteration 20 --no-bazel-mode \
        PinnedStackTests#testLaunchTaskByAffinityMatchSingleTask
Change-Id: I1ed848fcd742443a23ecaa17ba6b4fb8cdb061e2

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

@@ -1600,6 +1600,11 @@ public class PipTaskOrganizer implements ShellTaskOrganizer.TaskListener,
             // Avoid double removal, which is fatal.
             return;
         }
+        if (surface == null || !surface.isValid()) {
+            ProtoLog.w(ShellProtoLogGroup.WM_SHELL_PICTURE_IN_PICTURE,
+                    "%s: trying to remove invalid content overlay (%s)", TAG, surface);
+            return;
+        }
         final SurfaceControl.Transaction tx = mSurfaceControlTransactionFactory.getTransaction();
         tx.remove(surface);
         tx.apply();