fix import DSL install Github plugin failed (#16362)

web/service/use-plugins.ts

           if (item.type === 'github') {
             const data = item as GitHubItemAndMarketPlaceDependency
             // From local bundle don't have data.value.github_plugin_unique_identifier
-            if (!data.value.github_plugin_unique_identifier) {
+            uniqueIdentifier = data.value.github_plugin_unique_identifier!
+            if (!uniqueIdentifier) {
               const { unique_identifier } = await post<uploadGitHubResponse>('/workspaces/current/plugin/upload/github', {
                 body: {
                   repo: data.value.repo!,