Don't crash when omitting paint to drawBitmap() with A8 configs.

Change-Id: I3d630554ad82fa846385274d12d0434e890ef45d
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 6c454a4..a576548 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -1099,7 +1099,9 @@
 
     setupDraw();
     setupDrawWithTexture(true);
-    setupDrawAlpha8Color(paint->getColor(), alpha);
+    if (paint) {
+        setupDrawAlpha8Color(paint->getColor(), alpha);
+    }
     setupDrawColorFilter();
     setupDrawShader();
     setupDrawBlending(true, mode);