What a good bug report. I attach a patch which stops the crash, and leaves it up to the theme definition to enable the text area.
Index: splashy-0.3.13_patched/src/splashy_video.c =================================================================== --- splashy-0.3.13_patched.orig/src/splashy_video.c 2009-01-08 22:01:59.000000000 +1100 +++ splashy-0.3.13_patched/src/splashy_video.c 2009-01-08 22:04:35.000000000 +1100 @@ -145,7 +145,7 @@ * as F2 is pressed. Let's give'm a show for their * money! */ - if (visible) + if (visible && video.textbox) /* close #473230 thanks John Hughes */ { video.textbox->offscreen->Blit (video.textbox->surface, video.textbox->offscreen,