Revert of Don't allow nullptr in texels array params (unless using a transfer buffer).

src/gpu/vk/GrVkGpu.cpp

Index: src/gpu/vk/GrVkGpu.cpp
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index 4f4d7c99094ac9287a2f8a8620eb36a34e217bde..a208aed456405f8184f14cfc7eaed0e9c6dbda2b 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -542,8 +542,7 @@
     }
 
     // TODO: We're ignoring MIP levels here.
-    if (!texels.empty()) {
-        SkASSERT(texels.begin()->fPixels);
+    if (!texels.empty() && texels.begin()->fPixels) {
         if (!this->uploadTexData(tex, 0, 0, desc.fWidth, desc.fHeight, desc.fConfig,
                                  texels.begin()->fPixels, texels.begin()->fRowBytes)) {
             tex->unref();