Fix T84708: Versioning for Set Alpha node

The versioning code introduced in rB38df935c0985 skips the composite node
tree that is used by the scene thus not correctly versioning Set Alpha
nodes outside of node groups. This fix iterates through all node trees to
version all Set Alpha nodes.

Reviewed By: JacquesLucke

Differential Revision: https://developer.blender.org/D10110

source/blender/blenloader/intern/versioning_290.c

@@ -1504,7 +1504,7 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
 
   if (!MAIN_VERSION_ATLEAST(bmain, 292, 10)) {
     if (!DNA_struct_find(fd->filesdna, "NodeSetAlpha")) {
-      LISTBASE_FOREACH (bNodeTree *, ntree, &bmain->nodetrees) {
+      FOREACH_NODETREE_BEGIN (bmain, ntree, id) {
         if (ntree->type != NTREE_COMPOSIT) {
           continue;
         }
@@ -1517,6 +1517,7 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
           node->storage = storage;
         }
       }
+      FOREACH_NODETREE_END;
     }
 
     LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {