Renaming files in the Web IDE empties files (sometimes)

Summary

When renaming a file in the Web IDE, sometimes the file content is emptied.

Steps to reproduce

I'm trying to reproduce the problem, but I can't get to consistent steps to reproduce it.

Maybe related to gitlab-ce#51083 ?

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 16.04
Current User:	git
Using RVM:	no
Ruby Version:	2.4.4p296
Gem Version:	2.7.6
Bundler Version:1.16.2
Rake Version:	12.3.1
Redis Version:	3.2.11
Git Version:	2.18.0
Sidekiq Version:5.1.3
Go Version:	unknown
GitLab information
Version:	11.2.3
Revision:	06cbee3
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		https://gitlab.*****
HTTP Clone URL:	https://gitlab./some-group/some-project.git
SSH Clone URL:	git@**:some-group/some-project.git
Using LDAP:	yes
Using Omniauth:	no
GitLab Shell
Version:	8.1.1
Repository storage paths:
default: 	/var/opt/gitlab/git-data/repositories
Hooks:		/opt/gitlab/embedded/service/gitlab-shell/hooks
Git:		/opt/gitlab/embedded/bin/git