Prevent double selection of second split app

* Also fix small other bug where we were
checking only for LauncherState
OVERVIEW_SPLIT_SELECT and not for equivalent
3P RecentsState

Fixes: 227419997
Test: Repro steps don't cause bug. Yay.
Change-Id: Ibb8238185b959d22d8455b6812d29b2e268d9739

quickstep/src/com/android/quickstep/views/LauncherRecentsView.java

@@ -181,4 +181,9 @@ public class LauncherRecentsView extends RecentsView<BaseQuickstepLauncher, Laun
         super.initiateSplitSelect(splitSelectSource);
         mActivity.getStateManager().goToState(LauncherState.OVERVIEW_SPLIT_SELECT);
     }
+
+    @Override
+    protected boolean canLaunchFullscreenTask() {
+        return !mActivity.isInState(OVERVIEW_SPLIT_SELECT);
+    }
 }