Crash when clicking ssh jumplist item while there is opened window

As title says. SSH jumplist items work fine while there is no FluentTerminal window opened, but crash once there is at least one. Normal items (like CMD or PowerShell) open fine in both cases.

I have set FluentTerminal to open new tabs when there is an opened window.

Also, after crash, window size always resets to default size.

Reproduction:
1. Open FluentTerminal window (with CMD or PowerShell for example)
2. Right click on its icon on taskbar and click one of the SSH jumplist items
3. App crashes instead of opening that item in new tab

Stack trace:
```
System.NullReferenceException: Object reference not set to an instance of an object.
at FluentTerminal.App.ViewModels.MainViewModel.AddTabAsync(ShellProfile, String, Int32) + Oxdc
at FluentTerminal.App.ViewModels.MainViewModel.AddTabAsync(ShellProfile) + Ox3f
at FluentTerminal.App.App.d__36.MoveNext () + 0x2f4
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x21
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0x70
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task) + 0x38
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task) + 0x17
at System.Runtime.CompilerServices.TaskAwaiter.GetResult() + Oxb
at FluentTerminal.App.App.d__21.MoveNext() + 0x22c
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x21
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<>c. b__7_0(Object) + Ox1e
at System.Action`1.Invoke(T) + 0x28
at System.Threading.WinRTSynchronizationContext.Invoker.InvokeCore() + 0x33
```