Cannot choose branches in new merge request page

Summary

Cannot choose branch in merge request page(see screenshoot.) when I updated version from 10.7.5 to 10.8.3.(use omnibus). But I can type in the branch directly， its work.

Steps to reproduce

choose one project -> Merge Requset -> New Merge Request -> select source branch.

Example Project

none

What is the current bug behavior?

no branch can be selected

What is the expected correct behavior?

show all the branches

Relevant logs and/or screenshots

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		CentOS 7.4.1708
Current User:	git
Using RVM:	no
Ruby Version:	2.3.7p456
Gem Version:	2.6.14
Bundler Version:1.13.7
Rake Version:	12.3.1
Redis Version:	3.2.11
Git Version:	2.16.4
Sidekiq Version:5.0.5
Go Version:	unknown
GitLab information
Version:	10.8.3
Revision:	564c342
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		https://git.yingegou.com
HTTP Clone URL:	https://git.yingegou.com/some-group/some-project.git
SSH Clone URL:	git@git.yingegou.com:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	no
GitLab Shell
Version:	7.1.2
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 7.1.2 ? ... OK (7.1.2)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
1/1 ... ok
6/3 ... ok
32/4 ... ok
32/5 ... ok
32/6 ... ok
2/7 ... repository is empty
32/8 ... ok
8/9 ... repository is empty
32/10 ... ok
32/12 ... ok
32/13 ... ok
36/14 ... ok
30/15 ... ok
4/16 ... ok
38/18 ... ok
36/19 ... ok
36/20 ... ok
36/21 ... ok
41/22 ... ok
31/23 ... ok
35/24 ... ok
32/25 ... ok
36/26 ... ok
36/27 ... ok
36/28 ... ok
36/29 ... ok
36/30 ... ok
36/31 ... ok
36/32 ... ok
36/33 ... ok
36/34 ... ok
36/35 ... ok
36/36 ... ok
32/38 ... ok
32/39 ... ok
47/40 ... ok
47/41 ... ok
47/42 ... ok
47/43 ... ok
36/44 ... ok
49/45 ... repository is empty
2/46 ... ok
53/47 ... ok
2/48 ... ok
36/49 ... repository is empty
30/50 ... ok
25/52 ... repository is empty
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Reply by email is disabled in config/gitlab.yml
Checking LDAP ...
LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
1/1 ... yes
6/3 ... yes
32/4 ... yes
32/5 ... yes
32/6 ... yes
2/7 ... yes
32/8 ... yes
8/9 ... yes
32/10 ... yes
32/12 ... yes
32/13 ... yes
36/14 ... yes
30/15 ... yes
4/16 ... yes
38/18 ... yes
36/19 ... yes
36/20 ... yes
36/21 ... yes
41/22 ... yes
31/23 ... yes
35/24 ... yes
32/25 ... yes
36/26 ... yes
36/27 ... yes
36/28 ... yes
36/29 ... yes
36/30 ... yes
36/31 ... yes
36/32 ... yes
36/33 ... yes
36/34 ... yes
36/35 ... yes
36/36 ... yes
32/38 ... yes
32/39 ... yes
47/40 ... yes
47/41 ... yes
47/42 ... yes
47/43 ... yes
36/44 ... yes
49/45 ... yes
2/46 ... yes
53/47 ... yes
2/48 ... yes
36/49 ... yes
30/50 ... yes
25/52 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.3.7)
Git version >= 2.9.5 ? ... yes (2.16.4)
Git user has default SSH configuration? ... yes
Active users: ... 25
Checking GitLab ... Finished