Run shortcut can be activated before toolbox is loaded when initial workflow has build errors

[glopesdev]

Build errors thrown when loading the initial workflow will preempt the call to ShutdownSequence, which then enables the buttons and shortcuts, regardless of whether the toolbox has loaded or not:

bonsai/Bonsai.Editor/EditorForm.cs

Lines 1412 to 1414 in 43b16b9

	void HandleWorkflowError(Exception e)
	{
	var shutdown = ShutdownSequence();