fix: Initialised variable to keep CI from breaking (again).

src/package/vieter_package.c

@@ -185,7 +185,7 @@ char *vieter_package_to_description(vieter_package *pkg) {
   int i;
 
   // special case for FILENAME
-  char *ext;
+  char *ext = NULL;
   switch (pkg->compression) {
   case 0:
     ext = ".tar";