Only hide back button in SUW when ime is rendering it

Bug: 316482919
Test: Back button is visible in SUW when ime is not rendering it
Change-Id: Id3f5d637c9e459a1b7a766187f0c134dd39a05f9

quickstep/src/com/android/launcher3/taskbar/NavbarButtonsViewController.java

@@ -772,9 +772,11 @@ public class NavbarButtonsViewController implements TaskbarControllers.LoggableT
             handleSetupUi();
 
             // Hide back button in SUW if keyboard is showing (IME draws its own back).
-            mPropertyHolders.add(new StatePropertyHolder(
-                    mBackButtonAlpha.get(ALPHA_INDEX_SUW),
-                    flags -> (flags & FLAG_IME_VISIBLE) == 0));
+            if (mIsImeRenderingNavButtons) {
+                mPropertyHolders.add(new StatePropertyHolder(
+                        mBackButtonAlpha.get(ALPHA_INDEX_SUW),
+                        flags -> (flags & FLAG_IME_VISIBLE) == 0));
+            }
         } else if (isInKidsMode) {
             int iconSize = res.getDimensionPixelSize(
                     R.dimen.taskbar_icon_size_kids);