Change MarkedMessages to return uids

Especially if one tries to interact with all marked messages there could be
the case that not all headers are fetched yet, hence the messageInfo is still nil.

This segfaults a lot of commands which in principle only need the uid to complete.

If we switch to uids, this issue can be alleviated for those commands.

commands/msg/utils.go

@@ -18,12 +18,7 @@ func newHelper(aerc *widgets.Aerc) *helper {
 }
 
 func (h *helper) markedOrSelectedUids() ([]uint32, error) {
-	msgs, err := commands.MarkedOrSelected(h.msgProvider)
-	if err != nil {
-		return nil, err
-	}
-	uids := commands.UidsFromMessageInfos(msgs)
-	return uids, nil
+	return commands.MarkedOrSelected(h.msgProvider)
 }
 
 func (h *helper) store() (*lib.MessageStore, error) {
@@ -43,5 +38,13 @@ func (h *helper) account() (*widgets.AccountView, error) {
 }
 
 func (h *helper) messages() ([]*models.MessageInfo, error) {
-	return commands.MarkedOrSelected(h.msgProvider)
+	uid, err := commands.MarkedOrSelected(h.msgProvider)
+	if err != nil {
+		return nil, err
+	}
+	store, err := h.store()
+	if err != nil {
+		return nil, err
+	}
+	return commands.MsgInfoFromUids(store, uid)
 }