[wasm] sundry trap handler fixes

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index 9a777b20c69d50d19a952f6d443fd4cc91be00ca..6f4d09ddfcf14308b93b527e7f71ce21be440979 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -1316,7 +1316,7 @@ class WasmInstanceBuilder {
         }
 
         FixedArray* protected_instructions = code->protected_instructions();
-
+        DCHECK(protected_instructions != nullptr);
         Zone zone(isolate_->allocator(), "Wasm Module");
         ZoneVector<trap_handler::ProtectedInstructionData> unpacked(&zone);
         for (int i = 0; i < protected_instructions->length();