[wasm] Fix bounds check for zero initial memory.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index d202aadf7a141b167cf6a1bc608e2bc841b948f8..0a9c876aea608d83c17edaa0df1d81bc931ad93b 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -135,6 +135,11 @@ uint32_t RelocInfo::wasm_memory_size_reference() {
   return Memory::uint32_at(pc_);
 }
 
+uint8_t RelocInfo::wasm_memtype_size_reference() {
+  DCHECK(IsWasmMemtypeSizeReference(rmode_));
+  return Memory::uint8_at(pc_);
+}
+
 void RelocInfo::unchecked_update_wasm_memory_reference(
     Address address, ICacheFlushMode flush_mode) {
   Memory::Address_at(pc_) = address;