[makeotfexe] Extra glyph after mark to base rule is ignored

[khaledhosny]

The following does not produce any errors or warnings and the Y glyph is completely ignored (the output is the same with or without it):

markClass [acute grave] <anchor 150 -10> @TOP_MARKS;
lookup mark {
    position base X <anchor 250 450> mark @TOP_MARKS Y;
} mark;

Adding another glyph causes an error:

markClass [acute grave] <anchor 150 -10> @TOP_MARKS;
lookup mark {
    position base X <anchor 250 450> mark @TOP_MARKS Y Z;
} mark;

[khaledhosny]

The same happens with mark and ligature, but not with cursive which errors even with one glyph.