When you click the "Run all mutations" button and then immediately click the "Stop mutation run" button, 4 mutations are cancelled instead of the 3 ones that were running

[amulalic]

Reproduction instructions

1. Open the Visual Studio 2019
2. Mutate the whole solution using "Testura.muation" extension
3. Run all mutations and then immediately click the "Stop mutation run" button
   ==> 4 mutations are cancelled instead of the 3 ones that were running (see the video attached below).