With any branch right clicking > Create pull request... throws a null reference exception. Any branch state will cause this. Local, pushed, pending changes, etc.

ERROR [2016-02-16 13:29:42,592] [1] [SourceTree.Bookmarks.BookmarkManager] [RegisterBookmarkEventHandlers] - RegisterAsRepositoryUpdatedEventHandler called with null repo
ERROR [2016-02-16 13:29:48,546] [1] [SourceTree.AppRoot] [HandleCrash] - Fatal error
System.NullReferenceException: Object reference not set to an instance of an object.
at SourceTree.Repo.RepoHelper.CreatePullRequest(Repository repo, RepositoryRemoteProjectLink link, String remoteBranch, String commitSHA) in C:\projects\bitbucket.org\atlassian\sourcetreewin-prod\SourceTree.Api.UI.Wpf\Repo\RepoHelper.cs:line 798
at SourceTree.ViewModel.RepoTabViewModel.CreatePullRequestNoPrompt(String remote, String remoteBranch) in C:\projects\bitbucket.org\atlassian\sourcetreewin-prod\SourceTree.Api.UI.Wpf\ViewModel\RepoTabViewModel.cs:line 3838
at SourceTree.ViewModel.RepoTabViewModel.CreatePullRequestNoPromptIfNotAhead(String localBranch, String remote, String remoteBranch) in C:\projects\bitbucket.org\atlassian\sourcetreewin-prod\SourceTree.Api.UI.Wpf\ViewModel\RepoTabViewModel.cs:line 3870
at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
at System.Windows.Controls.MenuItem.InvokeClickAfterRender(Object arg)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)