You are out of disk space so the application is unable to save your changes.
Scroll down in the error message, and you'll see the following.
"ERROR: could not write to file "base/pgsql_tmp/pgsql_tmp8025.9.sharedfileset/i53of128.p1.0": No space left on device"
If you are hosting on the Mendix Cloud you will need to contact Mendix Support to upgrade your server with more storage capacity.
I hope this has helped. Good luck!