src: use MaybeLocal::FromMaybe to return exception

This commit suggests using MaybeLocal::FromMaybe to return the exception
string, passing in a default value (an empty Local<Value>) which will be
used if the exception object is empty.

PR-URL: #33514
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/api/environment.cc

@@ -48,17 +48,11 @@ static MaybeLocal<Value> PrepareStackTraceCallback(Local<Context> context,
                                       Local<Array> trace) {
   Environment* env = Environment::GetCurrent(context);
   if (env == nullptr) {
-    MaybeLocal<String> s = exception->ToString(context);
-    return s.IsEmpty() ?
-      MaybeLocal<Value>() :
-      MaybeLocal<Value>(s.ToLocalChecked());
+    return exception->ToString(context).FromMaybe(Local<Value>());
   }
   Local<Function> prepare = env->prepare_stack_trace_callback();
   if (prepare.IsEmpty()) {
-    MaybeLocal<String> s = exception->ToString(context);
-    return s.IsEmpty() ?
-      MaybeLocal<Value>() :
-      MaybeLocal<Value>(s.ToLocalChecked());
+    return exception->ToString(context).FromMaybe(Local<Value>());
   }
   Local<Value> args[] = {
       context->Global(),