My setup looks very similar except that I also have the user files absolute path specified. For mine I have it set to the file system path to this folder. If the file system path is the one specified in the error then you should be able to use a value like this:
I can get a similar error if I do not have both paths set accordingly. If this is not the file system path to this folder then you will need to get that first, and use it for this setting.