Issue #124, case 1: Added test for this case
Actual fix is in stx:libbasic, revision 3563e89f551b.
https://swing.fit.cvut.cz/projects/stx-jv/ticket/124#comment:19
/* XPM */
static char *CheckOffNext_xpm[] = {
/* width height ncolors chars_per_pixel */
"15 15 4 1",
/* colors */
"a c black",
"b c white",
"c c #555555",
"d c #aaaaaa",
/* pixels */
"dddddcccccddddd",
"dddccaaaaaccddd",
"ddcaadddddddcdd",
"dcacddddddddddd",
"dcadddddddddddd",
"caddddddddddddb",
"caddddddddddddb",
"caddddddddddddb",
"caddddddddddddb",
"caddddddddddddb",
"dccddddddddddbd",
"dcdddddddddddbd",
"ddcdddddddddbdd",
"ddddbdddddbbddd",
"dddddbbbbbddddd",
};