fix(VList): merge classes from itemProps

Author: KaelWD

packages/vuetify/src/components/VList/VListChildren.tsx

@@ -5,6 +5,7 @@ import { VListSubheader } from './VListSubheader'
 import { VDivider } from '@/components/VDivider'
 
 // Utilities
+import { mergeProps } from 'vue'
 import { createList } from './list'
 import { genericComponent, propsFactory } from '@/util'
 
@@ -73,11 +74,11 @@ export const VListChildren = genericComponent<new <T extends InternalListItem>(
         >
           {{
             activator: ({ props: activatorProps }) => {
-              const listItemProps = {
-                ...itemProps,
-                ...activatorProps,
-                value: props.returnObject ? item : itemProps.value,
-              }
+              const listItemProps = mergeProps(
+                itemProps,
+                activatorProps,
+                { value: props.returnObject ? item : itemProps.value }
+              ) as typeof itemProps
 
               return slots.header
                 ? slots.header({ props: listItemProps })