Marshall NULL strings without crashing

connection.c

@@ -338,7 +338,7 @@ wl_connection_vmarshal(struct wl_connection *connection,
 			break;
 		case 's':
 			s = va_arg(ap, const char *);
-			length = strlen(s);
+			length = s ? strlen(s) : 0;
 			*p++ = length;
 			memcpy(p, s, length);
 			p += DIV_ROUNDUP(length, sizeof(*p));
@@ -456,6 +456,9 @@ wl_connection_demarshal(struct wl_connection *connection,
 				goto out;
 			}
 
+			if (length == 0) {
+				values[i].string = NULL;
+			} else {
 				values[i].string = malloc(length + 1);
 				if (values[i].string == NULL) {
 					errno = ENOMEM;
@@ -464,6 +467,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 				}
 				memcpy(values[i].string, p, length);
 				values[i].string[length] = '\0';
+			}
 			p = next;
 			break;
 		case 'o':