fixed a small bug in dmenu when an empty font is supplied

config.mk

@@ -1,5 +1,5 @@
 # dmenu version
-VERSION = 3.0
+VERSION = 3.1
 
 # Customize below to fit your system
 

main.c

@@ -135,6 +135,8 @@ initfont(const char *fontstr) {
 	char *def, **missing;
 	int i, n;
 
+	if(!fontstr || fontstr[0] == '\0')
+		eprint("error, cannot load font: '%s'\n", fontstr);
 	missing = NULL;
 	if(dc.font.set)
 		XFreeFontSet(dpy, dc.font.set);