The behavior of this has improved (I'm using 6.4.78212).  Typing control-C
normally no longer displays an Uncaught Exception window.  However, if one
types control-C in the window from which estudio was started and then types
a second control-C after the Internal EiffelStudio Exception window is
displayed, then an Uncaught Exception window is displayed.  So there is still
a small bug here.