Fix compile error (uninitialized variable use)

src/gpu/vk/GrVkGpuCommandBuffer.cpp

Index: src/gpu/vk/GrVkGpuCommandBuffer.cpp
diff --git a/src/gpu/vk/GrVkGpuCommandBuffer.cpp b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
index e9a13d4517263709ad117dd0257acdd3a2e08c1e..f6104a33083693f28cca8a91c17b47bddaa260a7 100644
--- a/src/gpu/vk/GrVkGpuCommandBuffer.cpp
+++ b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
@@ -40,6 +40,11 @@ void get_vk_load_store_ops(GrGpuCommandBuffer::LoadAndStoreOp op,
             *loadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
             *storeOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
             break;
+        default:
+            SK_ABORT("Invalid LoadAndStoreOp");
+            *loadOp = VK_ATTACHMENT_LOAD_OP_LOAD;
+            *storeOp = VK_ATTACHMENT_STORE_OP_STORE;
+            break;
     }
 }