Fix vulkan compile

TBR=jvanverth@google.com
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2122263003

Review-Url: https://codereview.chromium.org/2122263003
diff --git a/src/gpu/vk/GrVkMemory.cpp b/src/gpu/vk/GrVkMemory.cpp
index 76b449c..63cb523 100644
--- a/src/gpu/vk/GrVkMemory.cpp
+++ b/src/gpu/vk/GrVkMemory.cpp
@@ -320,7 +320,7 @@
 #endif
         }
         fFreeSize -= alignedSize;
-        SkASSERT(allocSize > 0);
+        SkASSERT(*allocSize > 0);
 
         return true;
     }