While erasing stuff (black foreground, white background) with a mouse in the direction from top-left to bottom-right on a huge image, GIMP went unresponsive. The mouse cursor remained in the form of the cross with a rubber, and not only for GIMP, but also for the other applications in GNOME.  Other applications were responsive to the keyboard (but not to the mouse). I could still shut all the other applications down gracefully, and I had to kill GIMP (a GNOME dialog appeared that said that GIMP didn't react and offered me a kill option).
In the xterm from which GIMP was started (before I terminated this xterm), I saw this:
“
double free or corruption (!prev)
gimp: fatal error: Abgebrochen

”
I could still log out of GNOME and restart gdm3 after that.  Upon restarting GIMP, no recovery from autosave was offered.

It should be noted that erasing stuff GIMP usually works; it's a one-off exception with an unknown cause.

Please fix this.