Export request has dotx incorrect mimetype

When performing an export the request has ""application/vnd.openxmlformats-officedocument.wordprocessingml.document"" as content type for dotx files and it should be "application/vnd.openxmlformats-officedocument.wordprocessingml.template".
When performing an export if a client choose to directly open the document in browser instead of save the document, this bug will cause the browser to renaming the file to the specified content type. So a file with name "example.dotx" will be renamed to "example.dotx-1.docx" and Microsoft Office Word will show an error while opening the document.