Incorrect task progress for the building tree with PhyML

Scenario to reproduce:

1. Open "data/samples/CLUSTALW/HIV-1.aln".
2. Click the "Build tree" button on the main toolbar.
3. Select the "PhyML" tool, set "Equilibrium frequencies" option to "optimized", build the tree.
   Current state: build tree task has incorrect progress (see the attached screenshot).