If a module has no path setting, return an error.

clientserver.c

@@ -613,6 +613,11 @@ static int rsync_module(int f_in, int f_out, int i, const char *addr, const char
 	}
 
 	module_dir = lp_path(i);
+	if (*module_dir == '\0') {
+		rprintf(FLOG, "No path specified for module %s\n", name);
+		io_printf(f_out, "@ERROR: no path setting.\n");
+		return -1;
+	}
 	if (use_chroot) {
 		if ((p = strstr(module_dir, "/./")) != NULL) {
 			*p = '\0'; /* Temporary... */