LibJS: Don't assume non-empty [[Value]] in Completion TRY() helpers

Author: https://github.com/linusg
Commit: 95acb1ce88
Pull-request: https://github.com/SerenityOS/serenity/pull/11513
Reviewed-by: https://github.com/davidot ✅

Userland/Libraries/LibJS/Runtime/WeakMapConstructor.cpp

@@ -55,7 +55,7 @@ ThrowCompletionOr<Object*> WeakMapConstructor::construct(FunctionObject& new_tar
     if (!adder.is_function())
         return vm.throw_completion<TypeError>(global_object, ErrorType::NotAFunction, "'set' property of WeakMap");
 
-    TRY(get_iterator_values(global_object, vm.argument(0), [&](Value iterator_value) -> Optional<Completion> {
+    (void)TRY(get_iterator_values(global_object, vm.argument(0), [&](Value iterator_value) -> Optional<Completion> {
         if (!iterator_value.is_object())
             return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObject, String::formatted("Iterator value {}", iterator_value.to_string_without_side_effects()));