I want to delete the space in rubymine that is only space on the line when saving.

That's it
https://intellij-support.jetbrains.com/hc/en-us/community/posts/205803079-Configure-editor-to-remove-whitespaces-in-blank-lines

 Settings | Editor | General | Strip training spaces on Save

You can achieve this by changing the value of the

Sometimes, it can be handled as an empty line with no space.

RubyMine 2017.1.1
When I update to , sometimes I also have space left.

RubyMine automatically saves the file, but I don't think it's working. Cmd-s manually saves the space.