Add deferredList null check

Needed for non-deferred mode (debug.hwui.disable_draw_defer = true)

Change-Id: I278cbe200aa6ce06fa92dc45c63ceda6e85a0cbe
diff --git a/libs/hwui/DisplayList.cpp b/libs/hwui/DisplayList.cpp
index 744edca..bdd539e 100644
--- a/libs/hwui/DisplayList.cpp
+++ b/libs/hwui/DisplayList.cpp
@@ -381,8 +381,10 @@
         }
     }
     if (mAlpha < 1 && !mCaching) {
-        // flush since we'll either enter a Layer, or set alpha, both not supported in deferral
-        status |= deferredList->flush(renderer, dirty, flags, level);
+        if (deferredList) {
+            // flush since we'll either enter a Layer, or set alpha, both not supported in deferral
+            status |= deferredList->flush(renderer, dirty, flags, level);
+        }
 
         if (!mHasOverlappingRendering) {
             renderer.setAlpha(mAlpha);
@@ -399,7 +401,7 @@
         }
     }
     if (mClipChildren && !mCaching) {
-        if (CC_UNLIKELY(!renderer.hasRectToRectTransform())) {
+        if (deferredList && CC_UNLIKELY(!renderer.hasRectToRectTransform())) {
             // flush, since clip will likely be a region
             status |= deferredList->flush(renderer, dirty, flags, level);
         }