Branch protection affects wiki write permission

[maliffi]

• Gitea version (or commit ref): 1.9.0+rc2-2-g91e24a3a1
• Git version: 2.22.0
• Operating system:
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

2019/07/22 07:48:31 .../xorm/session_get.go:99:nocacheGet() [I] [SQL] SELECT `id`, `repo_id`, `branch_name`, `can_push`, `enable_whitelist`, `whitelist_user_i_ds`, `whitelist_team_i_ds`, `enable_merge_whitelist`, `merge_whitelist_user_i_ds`, `merge_whitelist_team_i_ds`, `approvals_whitelist_user_i_ds`, `approvals_whitelist_team_i_ds`, `required_approvals`, `created_unix`, `updated_unix` FROM `protected_branch` WHERE `repo_id`=? AND `branch_name`=? LIMIT 1 []interface {}{20, "master"}
2019/07/22 07:48:31 ...ters/private/hook.go:107:HookPreReceive() [W] Forbidden: User 23 cannot push to protected branch: master in 824713418768:Integrations/pvf
2019/07/22 07:48:31 models/wiki.go:222:updateWikiPage() [E] exit status 1 - remote: Gitea: protected branch master can not be pushed to
        To /data/git/repositories/integrations/pvf.wiki.git
         ! [remote rejected] 7bd77abfa7580be79b51fa4490fafefc697440d0 -> master (pre-receive hook declined)
        error: failed to push some refs to '/data/git/repositories/integrations/pvf.wiki.git'

2019/07/22 07:48:31 routers/repo/wiki.go:425:EditWikiPost() [E] EditWikiPage: Push: exit status 1 - remote: Gitea: protected branch master can not be pushed to
        To /data/git/repositories/integrations/pvf.wiki.git
         ! [remote rejected] 7bd77abfa7580be79b51fa4490fafefc697440d0 -> master (pre-receive hook declined)
        error: failed to push some refs to '/data/git/repositories/integrations/pvf.wiki.git'

Description

Got error 500 when you try to modify an existing pag einto Wiki or to create a new one.
The problem occurs only if on the default branch (usually "master") has active protection and the user attempting to modify the wiki page does not have permission to push/merge on master.
If the user permissions are modified to allow him to push on master, then he is able to modify/create wiki pages.