Fix issue with touches falling through nav bar in 3 button nav

- This fixes a regression from ag/17185260 where we are no longer
  returning early when computing the touchable region in different
  nav bar states.

Bug: 249053817
Test: Enable 3 button nav, dumpsys input and verify the touchable
      region matches the window frame
Change-Id: Ib5767494973bbb23b3125988b94dcf46a2a6df24

packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java

@@ -541,10 +541,12 @@ public class NavigationBar extends ViewController<NavigationBarView> implements
                 if (!mImeVisible) {
                     // IME not showing, take all touches
                     info.setTouchableInsets(InternalInsetsInfo.TOUCHABLE_INSETS_FRAME);
+                    return;
                 }
                 if (!mView.isImeRenderingNavButtons()) {
                     // IME showing but not drawing any buttons, take all touches
                     info.setTouchableInsets(InternalInsetsInfo.TOUCHABLE_INSETS_FRAME);
+                    return;
                 }
             }