Cleanup: use plural names for Main lists

Convention was not to but after discussion on 918941483f7e we agree its
best to change the convention.

Names now mostly follow RNA.

Some exceptions:

- Use 'nodetrees' instead of 'nodegroups'
  since the struct is called NodeTree.
- Use 'gpencils' instead of 'grease_pencil'
  since 'gpencil' is a common abbreviation in the C code.

Other exceptions:

- Leave 'wm' as it's a list of one.
- Leave 'ipo' as is for versioning.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/object/object_select.c b/source/blender/editors/object/object_select.c
index 96dc18b41f0..dd68c8d0357 100644
--- a/source/blender/editors/object/object_select.c
+++ b/source/blender/editors/object/object_select.c
@@ -788,7 +788,7 @@ static bool select_grouped_collection(bContext *C, Object *ob)
 	uiPopupMenu *pup;
 	uiLayout *layout;
 
-	for (collection = CTX_data_main(C)->collection.first; collection && collection_count < COLLECTION_MENU_MAX; collection = collection->id.next) {
+	for (collection = CTX_data_main(C)->collections.first; collection && collection_count < COLLECTION_MENU_MAX; collection = collection->id.next) {
 		if (BKE_collection_has_object(collection, ob)) {
 			ob_collections[collection_count] = collection;
 			collection_count++;