Fixing nullPointer exception when wallpaper colors is null

Bug: 186722571
Test: Presubmit
Change-Id: Iee0d15d460de47cc20395cf9f3d92784aef6268e
diff --git a/src/com/android/launcher3/util/Themes.java b/src/com/android/launcher3/util/Themes.java
index 11b856e..99942aa 100644
--- a/src/com/android/launcher3/util/Themes.java
+++ b/src/com/android/launcher3/util/Themes.java
@@ -19,6 +19,7 @@
 import static android.app.WallpaperColors.HINT_SUPPORTS_DARK_TEXT;
 import static android.app.WallpaperColors.HINT_SUPPORTS_DARK_THEME;
 
+import android.app.WallpaperColors;
 import android.app.WallpaperManager;
 import android.content.Context;
 import android.content.res.Configuration;
@@ -41,9 +42,14 @@
 public class Themes {
 
     public static int getActivityThemeRes(Context context) {
-        int colorHints = Utilities.ATLEAST_P ? context.getSystemService(WallpaperManager.class)
-                .getWallpaperColors(WallpaperManager.FLAG_SYSTEM).getColorHints()
-                : 0;
+        final int colorHints;
+        if (Utilities.ATLEAST_P) {
+            WallpaperColors colors = context.getSystemService(WallpaperManager.class)
+                    .getWallpaperColors(WallpaperManager.FLAG_SYSTEM);
+            colorHints = colors == null ? 0 : colors.getColorHints();
+        } else {
+            colorHints = 0;
+        }
         return getActivityThemeRes(context, colorHints);
     }