ref: Fix crash if serve gets called before logging in

The existing check did not exit the function after detecting the
error.

Change-Id: Ie2f3f334c6f69f5d516a606c77b614669d325f64
diff --git a/services/syncbase/bridge/cgo/impl.go b/services/syncbase/bridge/cgo/impl.go
index 1d7e620..8131637 100644
--- a/services/syncbase/bridge/cgo/impl.go
+++ b/services/syncbase/bridge/cgo/impl.go
@@ -185,6 +185,7 @@
 func v23_syncbase_Serve(cErr *C.v23_syncbase_VError) {
 	if !isLoggedIn() {
 		cErr.init(verror.New(verror.ErrInternal, nil, "not logged in"))
+		return
 	}
 	srv, disp, cleanup := syncbaselib.Serve(b.Ctx, syncbaselib.Opts{
 		RootDir: fmt.Sprintf("%s/db", rootDir),