fix(login v1): handle old sessions in logout (#10926)

# Which Problems Are Solved

Sessions created through login UI (v1) automatically get assigned an ID
after creation. This change was introduced with the OIDC back-channel
logout implementation. Sessions created before that don't have an ID and
are updated on the next (re-)authentication.
A customer now reached out, that a logout from Console was resulting in
an error. This is due to at least one session not having an ID (<null>
in sql) in the same user agent.

# How the Problems Are Solved

Since the sessionID is not used in the specific situation, we just
assign the userID as sessionID. This way all sessions are properly
terminated.

# Additional Changes

None

# Additional Context

- relates to support request
- requires backport to v4.x

internal/user/repository/view/user_session_view.go

@@ -100,7 +100,8 @@ func ActiveUserSessionsBySessionID(ctx context.Context, db *database.DB, session
 func scanActiveUserAgentUserIDs(rows *sql.Rows) (userAgentID string, sessions map[string]string, err error) {
 	sessions = make(map[string]string)
 	for rows.Next() {
-		var userID, sessionID string
+		var userID string
+		var sessionID sql.NullString
 		err := rows.Scan(
 			&userAgentID,
 			&userID,
@@ -109,7 +110,14 @@ func scanActiveUserAgentUserIDs(rows *sql.Rows) (userAgentID string, sessions ma
 		if err != nil {
 			return "", nil, err
 		}
-		sessions[sessionID] = userID
+		// Sessions created before back-channel logout implementation and never updated
+		// since then, don't have an ID.
+		// In this case, we use the userID as sessionID to ensure uniqueness in the map.
+		// The ID will not be used for logout process itself.
+		if !sessionID.Valid {
+			sessionID.String = userID
+		}
+		sessions[sessionID.String] = userID
 	}
 	if err := rows.Close(); err != nil {
 		return "", nil, zerrors.ThrowInternal(err, "VIEW-Sbrws", "Errors.Query.CloseRows")