Fix crash when loading string cache

Crash was caused by a null context in ModelDelegate

Fixes: 218305827
Test: manual
Change-Id: I1b046e24427dbdc6752ac100f488c428838ac31f

src/com/android/launcher3/graphics/PreviewSurfaceRenderer.java

@@ -47,7 +47,6 @@ import com.android.launcher3.graphics.LauncherPreviewRenderer.PreviewContext;
 import com.android.launcher3.model.BgDataModel;
 import com.android.launcher3.model.GridSizeMigrationTaskV2;
 import com.android.launcher3.model.LoaderTask;
-import com.android.launcher3.model.ModelDelegate;
 import com.android.launcher3.util.ComponentKey;
 import com.android.launcher3.util.RunnableList;
 import com.android.launcher3.util.Themes;
@@ -156,9 +155,10 @@ public class PreviewSurfaceRenderer {
             PreviewContext previewContext = new PreviewContext(inflationContext, mIdp);
             new LoaderTask(
                     LauncherAppState.getInstance(previewContext),
-                    null,
+                    /* bgAllAppsList= */ null,
                     new BgDataModel(),
-                    new ModelDelegate(), null) {
+                    LauncherAppState.getInstance(previewContext).getModel().getModelDelegate(),
+                    /* results= */ null) {
 
                 @Override
                 public void run() {

src/com/android/launcher3/model/ModelDelegate.java

@@ -44,11 +44,7 @@ public class ModelDelegate implements ResourceBasedOverride {
             boolean isPrimaryInstance) {
         ModelDelegate delegate = Overrides.getObject(
                 ModelDelegate.class, context, R.string.model_delegate_class);
-        delegate.mApp = app;
-        delegate.mAppsList = appsList;
-        delegate.mDataModel = dataModel;
-        delegate.mIsPrimaryInstance = isPrimaryInstance;
-        delegate.mContext = context;
+        delegate.init(context, app, appsList, dataModel, isPrimaryInstance);
         return delegate;
     }
 
@@ -60,6 +56,18 @@ public class ModelDelegate implements ResourceBasedOverride {
 
     public ModelDelegate() { }
 
+    /**
+     * Initializes the object with the given params.
+     */
+    private void init(Context context, LauncherAppState app, AllAppsList appsList,
+            BgDataModel dataModel, boolean isPrimaryInstance) {
+        this.mApp = app;
+        this.mAppsList = appsList;
+        this.mDataModel = dataModel;
+        this.mIsPrimaryInstance = isPrimaryInstance;
+        this.mContext = context;
+    }
+
     /**
      * Called periodically to validate and update any data
      */