Zero-length string is not a valid real name.

src/sbbs3/userdat.c

@@ -3873,6 +3873,8 @@ bool check_realname(scfg_t* cfg, const char* name)
 {
 	if (name == NULL)
 		return false;
+	if (name[0] == 0)
+		return false;
 
 	return (uchar)name[0] < 0x7f && name[1] && IS_ALPHA(name[0]) && strchr(name, ' ');
 }