With #602, if proxy and pruning settings are disabled in the GUI and the GUI is restarted, proxy and prune values are not stored anywhere. So if these settings are enabled in the future, default values will be shown, not previous values.
This PR stores previous values so they will preserved across restarts. I’m not sure I like this behavior because showing default values seems simpler and safer to me. Previous values may just have been set temporarily and may have never actually worked, and it adds some code complexity to store them.
This PR is one way of resolving #596. Other solutions are possible and could be implemented as alternatives.