Also protect against malformed GfxPatchMeshShading

oss-fuzz/11197
7 jobs for validity_check in 6 minutes and 21 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #6539783
build

00:06:21

passed #6539788
build_android

00:00:56

passed #6539784
build_clang_libcpp

00:04:46

passed #6539787
build_clazy

00:04:18

passed #6539786
build_mingw64_fedora

00:02:56

passed #6539785
build_ubuntu_16_04

00:03:32

passed #6539782
clang_format

00:01:19