WireServer: don't skip destroy on error objects.

An old-style builder might become an error object when a
validation error occurs on one of its methods. It still has
to be freed, so the correct check for "destroy" is to check
that the handle is not null.

BUG=chromium:914819
BUG=chromium:914867
BUG=chromium:914964
BUG=chromium:915083

Change-Id: I349faffa48f369b72c603d47dd23ffae7d86891e
Reviewed-on: https://dawn-review.googlesource.com/c/3323
Reviewed-by: Stephen White <senorblanco@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

generator/templates/dawn_wire/WireServer.cpp

@@ -655,7 +655,7 @@ namespace dawn_wire {
                             m{{type.name.CamelCase()}}IdTable.Remove(data->handle);
                         {% endif %}
 
-                        if (data->valid) {
+                        if (data->handle != nullptr) {
                             mProcs.{{as_varName(type.name, Name("release"))}}(data->handle);
                         }