Nasrani is Arabic for Christians (though it may refer directly to Arab Christians, not "Christians" in arabic). They should fight with mass fire only as a sort of "levy line" option for Muslim invaders.
Morocco and non-ottoman expansion into Europe will be getting tweaked a bit soon. Not repolished per se (which insinutates a complete revamp), but I came into very valuable and extensive information which better explains the nature of Muslim-Christian relations in fighting together.
Good note of the bug, we'll look into that.