If the autocompletion list is invoked a second time - say, first typing s on the text editor, erasing and then typing s again - the application will crash and close at once.
I'm using Linux Mint 18 Cinnamon 64-bits. I installed SpeedCrunch from the 64-bit DEB file, but the problem persists with the .tar.bz2 binary. A friend of mine, using the same Mint system, reported no issues.
Execution of the application through the terminal generates the text output in the attached screenshot after reproducing the error.
Edit: Text file is gdb log when reproducing the error on a debug build.