Skip drawing snapshot if we can't create the buffer.

Bug: 63436798
Test: Only a NPE check
Change-Id: I1c87d9dfcf828e3c7d4fb070e7492834761224e7

services/core/java/com/android/server/wm/TaskSnapshotController.java

@@ -296,7 +296,9 @@ class TaskSnapshotController {
         decorPainter.drawDecors(c, null /* statusBarExcludeFrame */);
         node.end(c);
         final Bitmap hwBitmap = ThreadedRenderer.createHardwareBitmap(node, width, height);
-
+        if (hwBitmap == null) {
+            return null;
+        }
         return new TaskSnapshot(hwBitmap.createGraphicBufferHandle(),
                 topChild.getConfiguration().orientation, mainWindow.mStableInsets,
                 ActivityManager.isLowRamDeviceStatic() /* reduced */, 1.0f /* scale */);