fix(ServeConfigModel.init): invoke callBack when server is null

app/src/main/java/io/legado/app/ui/book/import/remote/ServerConfigViewModel.kt

@@ -19,11 +19,9 @@ class ServerConfigViewModel(application: Application): BaseViewModel(application
                 null
             }
         }.onSuccess {
-            if (it != null) {
             onSuccess.invoke()
         }
     }
-    }
 
     fun save(server: Server, onSuccess: () -> Unit) {
         execute {