Belt and suspenders for colors in DrawAtlasBatch test

src/gpu/batches/GrDrawAtlasBatch.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDrawAtlasBatch.h"
 #include "GrBatchTest.h"
 #include "SkGr.h"
@@ skipping 233 matching lines @@
                      random,
                      &xforms,
                      &texRects,
                      &colors, hasColors);
     
     SkMatrix viewMatrix = GrTest::TestMatrix(random);
     
     GrDrawAtlasBatch::Geometry geometry;
     geometry.fColor = GrRandomColor(random);
     return GrDrawAtlasBatch::Create(geometry, viewMatrix, spriteCount, xforms.begin(),
-                                    texRects.begin(), colors.begin());
+                                    texRects.begin(), hasColors ? colors.begin() : nullptr);
 }
 
 #endif