Do not finish activity onBackPressed.

Fixes: 132282437
Test: open app, tap back, enter through overview
Change-Id: Ie6d7f30a58429521c3a5c03f95410c1035189713
diff --git a/src/com/android/customization/picker/CustomizationPickerActivity.java b/src/com/android/customization/picker/CustomizationPickerActivity.java
index c20b73f..8759dab 100644
--- a/src/com/android/customization/picker/CustomizationPickerActivity.java
+++ b/src/com/android/customization/picker/CustomizationPickerActivity.java
@@ -266,6 +266,17 @@
         }
     }
 
+    @Override
+    public void onBackPressed() {
+        if (getSupportFragmentManager().popBackStackImmediate()) {
+            return;
+        }
+        if (moveTaskToBack(false)) {
+            return;
+        }
+        super.onBackPressed();
+    }
+
     private void navigateToSection(@IdRes int id) {
         mBottomNav.setSelectedItemId(id);
     }