lib/model: Create root directory for paused folders (fixes #4094)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4095

cmd/syncthing/main.go

@@ -815,6 +815,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	// Add and start folders
 	for _, folderCfg := range cfg.Folders() {
 		if folderCfg.Paused {
+			folderCfg.CreateRoot()
 			continue
 		}
 		m.AddFolder(folderCfg)