Crash when run from a git worktree

[laurentkempe]

Running git pr from a git worktree output the following

Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentNullException: Value cannot be null.                                                                                    
Parameter name: key                                                                                                                                                                                                                                                     
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)                                                                                                                                                                                                       
   at System.Collections.Generic.Dictionary`2.ContainsKey(TKey key)                                                                                                                                                                                                     
   at GitPullRequest.Services.RemoteRepositoryCache.FindRemoteRepository(String remoteName) in C:\Source\github.com\jcansdale\GitPullRequest\GitPullRequest.Services\RemoteRepositoryCache.cs:line 27                                                                   
   at GitPullRequest.Services.GitPullRequestService.FindPullRequests(RemoteRepositoryCache remoteRepositoryCache, IList`1 upstreamRepositories, Branch branch) in C:\Source\github.com\jcansdale\GitPullRequest\GitPullRequest.Services\GitPullRequestService.cs:line 31
   at GitPullRequest.Program.BrowsePullRequest(GitPullRequestService service, Repository repo, Action`1 exceptionLogger) in C:\Source\github.com\jcansdale\GitPullRequest\GitPullRequest\Program.cs:line 83                                                             
   at GitPullRequest.Program.OnExecute() in C:\Source\github.com\jcansdale\GitPullRequest\GitPullRequest\Program.cs:line 68                                                                                                                                             
   --- End of inner exception stack trace ---                                                                                                                                                                                                                           
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)                                                                                                                            
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)                                                                                                                          
   at McMaster.Extensions.CommandLineUtils.Conventions.ExecuteMethodConvention.Invoke(MethodInfo method, Object instance, Object[] arguments) in C:\projects\commandlineutils\src\CommandLineUtils\Conventions\ExecuteMethodConvention.cs:line 86                       
   at McMaster.Extensions.CommandLineUtils.Conventions.ExecuteMethodConvention.OnExecute(ConventionContext context) in C:\projects\commandlineutils\src\CommandLineUtils\Conventions\ExecuteMethodConvention.cs:line 64                                                 
   at McMaster.Extensions.CommandLineUtils.Conventions.ExecuteMethodConvention.<>c__DisplayClass0_0.<<Apply>b__0>d.MoveNext() in C:\projects\commandlineutils\src\CommandLineUtils\Conventions\ExecuteMethodConvention.cs:line 25                                       
--- End of stack trace from previous location where exception was thrown ---                                                                                                                                                                                            
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.<>c__DisplayClass131_0.<OnExecute>b__0() in C:\projects\commandlineutils\src\CommandLineUtils\CommandLineApplication.cs:line 600                                                                      
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute[TApp](CommandLineContext context) in C:\projects\commandlineutils\src\CommandLineUtils\CommandLineApplication.Execute.cs:line 31                                                              
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute[TApp](IConsole console, String[] args) in C:\projects\commandlineutils\src\CommandLineUtils\CommandLineApplication.Execute.cs:line 105                                                        
   at GitPullRequest.Program.Main(String[] args) in C:\Source\github.com\jcansdale\GitPullRequest\GitPullRequest\Program.cs:line 18