[FIX] Unwanted toastr error message when deleting user (#23372)

* check if user exists when accessing canViewAllInfo

* Explicitly return null

Co-authored-by: Tasso Evangelista <tasso.evangelista@rocket.chat>

app/lib/server/functions/getFullUserData.js

@@ -89,6 +89,10 @@ export function getFullUserDataByIdOrUsername({ userId, filterId, filterUsername
 		fields,
 	};
 	const user = Users.findOneByIdOrUsername(filterId || filterUsername, options);
+	if (!user) {
+		return null;
+	}
+
 	user.canViewAllInfo = canViewAllInfo;
 
 	return myself ? user : removePasswordInfo(user);