PostController: editing a discussion or poll would result in a hidden CategoryID input with an empty value whenever 'Display root categories as headings' was checked. This did not cause issues when editing a regular discussion, which was fortunate, but when editing a poll the form would error out due to a null CategoryID.
Merge branch 'stage' of github.com:vanilla/vanilla into feature/postcontroller-fix
Merge pull request #2000 from vanilla/feature/postcontroller-fix

PostController: editing a discussion or poll would result in a missing CategoryID error
Activity: Add check to target before redirection.
Activity: Refactor IsSafeLink to IsSafeUrl.
Activity: Refactor to IsSafeUrl to not call get twice.
Activity: Improve IsSafeUrl.
Activity: Optimize IsSafeUrl.
Merge branch 'master' into stage
Fix Disqus CSS typo.
Merge pull request #2001 from vanilla/hotfix/burp

Activity: Add check to target before redirection.
Remove the .travis.yml.
Emoji: Fix to use proper path.
Merge branch 'master' of github.com:vanilla/vanilla into stage
Allow Gdn_Request::Url() to take ‘https’ as an argument for $WithDomain.
Merge branch 'stage' of github.com:vanilla/vanilla into stage
Merge branch 'master' into stage
Show the default locale in the locale settings data.
Add the remove share image endpoint.
Allow the default configuration path to be set by code.