VMWare Fusion OS X 10.13.5 GUID partition
Restart the system in single user mode.

To restart your system in single user mode, restart your Mac and as soon as it turns off and is about to start, press and hold CMD + S buttons.

You should see a command prompt logged in as root.

Now, run the following command:

/sbin/fsck -fy


if your drive was OK, the screen will say “The volume (name of your hard drive) appears to be OK”. If any repair was made, you’ll see the prompt, “FILE SYSTEM WAS MODIFIED”. Then, you’ll see the root# prompt again.

Then try to restart the system and try deleting the space. It should work. If not, you'll have to use the diskutil command to override this thing and get it to work. 

In case the solutions I've provided here is not working for you, please do this:

Reboot your mac in Recovery mode(While rebooting hold CMD + R), launch terminal and run diskutil list and update your question with the screenshot.