Fix nullptr-deref when command buffer init fails

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index fd344da67705e2a84f1f565cbcff5613b0f8d7ec..b026052bbbe3b55b417936acd33350d5b313b2f4 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -429,7 +429,7 @@ void GpuCommandBufferStub::Destroy() {
   scheduler_.reset();
 
   bool have_context = false;
-  if (decoder_) {
+  if (decoder_ && decoder_->GetGLContext()) {
     // Try to make the context current regardless of whether it was lost, so we
     // don't leak resources.
     have_context = decoder_->GetGLContext()->MakeCurrent(surface_.get());