fix race condition in photo dreams settings activity

Bug: 11225307
Change-Id: I7e52c83e172aa2e1418344fc14d438644d54dd07
diff --git a/src/com/android/dreams/phototable/FlipperDreamSettings.java b/src/com/android/dreams/phototable/FlipperDreamSettings.java
index 464029e..cd24721 100644
--- a/src/com/android/dreams/phototable/FlipperDreamSettings.java
+++ b/src/com/android/dreams/phototable/FlipperDreamSettings.java
@@ -108,7 +108,9 @@
     public boolean onOptionsItemSelected(MenuItem item) {
         switch (item.getItemId()) {
         case R.id.photodream_menu_all:
-            mAdapter.selectAll(!mAdapter.areAllSelected());
+            if (mAdapter != null) {
+                mAdapter.selectAll(!mAdapter.areAllSelected());
+            }
             return true;
         default:
             return super.onOptionsItemSelected(item);