fix(SelectMenu): wrong placeholder color when modelValue is an empt…

…y string

Resolves #1862

src/runtime/components/forms/SelectMenu.vue

@@ -391,7 +391,7 @@ export default defineComponent({
         variant?.replaceAll('{color}', color.value),
         (isLeading.value || slots.leading) && ui.value.leading.padding[size.value],
         (isTrailing.value || slots.trailing) && ui.value.trailing.padding[size.value]
-      ), props.placeholder && (props.modelValue === undefined && props.modelValue === null) && ui.value.placeholder, props.selectClass)
+      ), props.placeholder && !props.modelValue && ui.value.placeholder, props.selectClass)
     })
 
     const isLeading = computed(() => {