allow 0 nmaster

dwm.c

@@ -1028,7 +1028,7 @@ grabkeys(void) {
 
 void
 incnmaster(const Arg *arg) {
-	selmon->nmaster = MAX(selmon->nmaster + arg->i, 1);
+	selmon->nmaster = MAX(selmon->nmaster + arg->i, 0);
 	arrange(selmon);
 }
 
@@ -1666,8 +1666,10 @@ tile(Monitor *m) {
 	if(n == 0)
 		return;
 
-	mw = (n > m->nmaster) ? m->ww * m->mfact : m->ww;
-
+	if(n > m->nmaster)
+		mw = m->nmaster ? m->ww * m->mfact : 0;
+	else
+		mw = m->ww;
 	for(i = my = ty = 0, c = nexttiled(m->clients); c; c = nexttiled(c->next), i++)
 		if(i < m->nmaster) {
 			h = (m->wh - my) / (MIN(n, m->nmaster) - i);