fix(files_sharing): only show "shared with me" information if shared

The variable is intialized to `{}` which is truthy, so instead just

check if there is a user assigned to the share info.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

[skip ci]

Author: susnux

apps/files_sharing/src/views/SharingTab.vue

@@ -240,8 +240,7 @@ export default {
 		 * @return {boolean}
 		 */
 		isSharedWithMe() {
-			return this.sharedWithMe !== null
-				&& this.sharedWithMe !== undefined
+			return !!this.sharedWithMe?.user
 		},
 
 		/**