Fix nullptr access in GrTextureProvider::createMipMappedTexture

src/gpu/GrTextureProvider.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 "GrTextureProvider.h"
 #include "GrTexturePriv.h"
 #include "GrResourceCache.h"
@@ skipping 35 matching lines @@
         }
     }
 
     if ((desc.fFlags & kRenderTarget_GrSurfaceFlag) &&
         !fGpu->caps()->isConfigRenderable(desc.fConfig, desc.fSampleCnt > 0)) {
         return nullptr;
     }
     if (!GrPixelConfigIsCompressed(desc.fConfig) &&
         !desc.fTextureStorageAllocator.fAllocateTextureStorage) {
         if (mipLevelCount < 2) {
-            const GrMipLevel& baseMipLevel = texels[0];
+            const void* basePixels = nullptr;
+            size_t baseRowBytes = 0;
+            if (1 == mipLevelCount) {
+                basePixels = texels[0].fPixels;
+                baseRowBytes = texels[0].fRowBytes;
+            }
             static const uint32_t kFlags = kExact_ScratchTextureFlag |
                                            kNoCreate_ScratchTextureFlag;
             if (GrTexture* texture = this->refScratchTexture(desc, kFlags)) {
                 if (!texels || texture->writePixels(0, 0, desc.fWidth, desc.fHeight, desc.fConfig,
-                                                    baseMipLevel.fPixels, baseMipLevel.fRowBytes)) {
+                                                    basePixels, baseRowBytes)) {
                     if (SkBudgeted::kNo == budgeted) {
                         texture->resourcePriv().makeUnbudgeted();
                     }
                     return texture;
                 }
                 texture->unref();
             }
         }
     }
 
@@ skipping 120 matching lines @@
 GrTexture* GrTextureProvider::findAndRefTextureByUniqueKey(const GrUniqueKey& key) {
     ASSERT_SINGLE_OWNER
     GrGpuResource* resource = this->findAndRefResourceByUniqueKey(key);
     if (resource) {
         GrTexture* texture = static_cast<GrSurface*>(resource)->asTexture();
         SkASSERT(texture);
         return texture;
     }
     return NULL;
 }