修复

app/views/repositories/_simple_entry.json.jbuilder

@@ -7,7 +7,7 @@ if @project.forge?
   json.sha entry['sha']
   json.path entry['path']
   json.type entry['type']
-  json.submodule_git_url repo_git_submodule_url(@owner, @repository, entry['submodule_git_url'])
+  json.submodule_git_url entry['submodule_git_url'].nil? ? nil : repo_git_submodule_url(@owner, @repository, entry['submodule_git_url'])
   json.size entry['size']
   is_readme = is_readme?(entry['type'], entry['name'])
   if is_readme 

app/views/repositories/entries.json.jbuilder

@@ -51,7 +51,7 @@ if @project.forge?
       json.path entry['path']
       json.sha entry['sha']
       json.type entry['type']
-      json.submodule_git_url repo_git_submodule_url(@owner, @repository, entry['submodule_git_url'])
+      json.submodule_git_url entry['submodule_git_url'].nil? ? nil : repo_git_submodule_url(@owner, @repository, entry['submodule_git_url'])
       json.size entry['size']
       json.is_readme_file is_readme?(entry['type'], entry['name'])
       json.content decode64_content(entry, @owner, @repository, @ref, @path)