Fix crash when divider receives imetarget that isn't in a split

Bug: 149828540
Test: Can use ime on keyguard
Change-Id: Iae7007d6c8157cffd821e2372d19b27df869d6c7
diff --git a/packages/SystemUI/src/com/android/systemui/stackdivider/Divider.java b/packages/SystemUI/src/com/android/systemui/stackdivider/Divider.java
index 2daefbd..56cdff4 100644
--- a/packages/SystemUI/src/com/android/systemui/stackdivider/Divider.java
+++ b/packages/SystemUI/src/com/android/systemui/stackdivider/Divider.java
@@ -137,7 +137,8 @@
                         try {
                             mLastImeTarget = ActivityTaskManager.getTaskOrganizerController()
                                     .getImeTarget(displayId);
-                            mShouldAdjustForIme = !mSplitLayout.mDisplayLayout.isLandscape()
+                            mShouldAdjustForIme = mLastImeTarget != null
+                                    && !mSplitLayout.mDisplayLayout.isLandscape()
                                     && (mLastImeTarget.asBinder()
                                     == mSplits.mSecondary.token.asBinder());
                         } catch (RemoteException e) {