sds.c/sdscatvprintf: set va_end to finish va_list cpy

src/sds.c

@@ -390,7 +390,7 @@ sds sdscatvprintf(sds s, const char *fmt, va_list ap) {
         buf[buflen-2] = '\0';
         va_copy(cpy,ap);
         vsnprintf(buf, buflen, fmt, cpy);
-        va_end(ap);
+        va_end(cpy);
         if (buf[buflen-2] != '\0') {
             if (buf != staticbuf) zfree(buf);
             buflen *= 2;