Regression in Datagrid behaviour

[MarkusKgit]

Bug explanation

Hi there,

after upgrading from 4.5.0 to 4.6.1 I noticed a change in behaviour of the Datagrid:
I have a DataGrid with a DataGridTemplateColumn containing a Button that is bound to a command of the child VM. Before 4.6.0/4.6.1 command execution was working fine on first click of the Button but now the first click is ignored (as if the row needs to be selected first). You can see it here:
Previous behaviour (which is also vanilla WPF behaviour):

Current behaviour:

I created a (somewhat) minimal repro

Version

4.6.1