Fix main stage full screen after lock phone

We will set main stage to full screen when it visible but side
stage not visible, but we should not do it when phone unlock.
Add isSleeping check to avoid such problem.

Fix: 193605614
Test: pick any 2 apps to stage split then lock and unlock phone.
Change-Id: I0fd99960ca0c5a10ac33b23f92f01d9b48877379

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java

@@ -526,9 +526,10 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                 // visible.
                 mMainStage.updateConfiguration(
                         WINDOWING_MODE_MULTI_WINDOW, getMainStageBounds(), wct);
-            } else {
+            } else if (!mSideStage.mRootTaskInfo.isSleeping) {
                 // We want the main stage configuration to be fullscreen when the side stage isn't
                 // visible.
+                // We should not do it when side stage are not visible due to sleeping display too.
                 mMainStage.updateConfiguration(WINDOWING_MODE_FULLSCREEN, null, wct);
             }
             // TODO: Change to `mSyncQueue.queue(wct)` once BLAST is stable.