This is a bug in Studio Pro. Most of the times that I have seen this popup, it went away after actions like clearing the deployment directory, closing the project, restarting the laptop, re-install Studio Pro it went away. Exactly like Parth Mishra said. Luckily I have not seen this popup often.
Alternative is to upgrade to 8.13.2, which is advisable anyway since it is a bugfix release.
Alternative is to upgrade to 8.17.0, which is advisable as well since Mendix recently adviced to move up to this version, for apps above 8.12.5.
And if after all this, you keep having this problem, raise a ticket via email@example.com, or support.mendix.com passing along your project mpk