Fix condition for memory allocation to check for nullopt.

Bug: chromium:1394660
Change-Id: I54b395728c5a857fdcbff6a0f1c05c8db6051e5a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/112443
Commit-Queue: Loko Kung <lokokung@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>

src/dawn/wire/BufferConsumer_impl.h

@@ -54,7 +54,7 @@ WireResult BufferConsumer<BufferT>::NextN(N count, T** data) {
 
     // If size is zero then it indicates an overflow.
     auto size = WireAlignSizeofN<T>(count);
-    if (size && *size > mSize) {
+    if (!size || *size > mSize) {
         return WireResult::FatalError;
     }