fix(Alert): remove required title to prevent warning when using slot

src/runtime/components/elements/Alert.vue

@@ -5,7 +5,7 @@
       <UAvatar v-if="avatar" v-bind="{ size: ui.avatar.size, ...avatar }" :class="ui.avatar.base" />
 
       <div :class="ui.inner">
-        <p :class="ui.title">
+        <p v-if="(title || $slots.title)" :class="ui.title">
           <slot name="title" :title="title">
             {{ title }}
           </slot>
@@ -57,7 +57,7 @@ export default defineComponent({
   props: {
     title: {
       type: String,
-      required: true
+      default: null
     },
     description: {
       type: String,