After U33.1 removed aggressive stance from Captain and Lore-master companions, a skill slot is left empty at the end of the pet shortcut bar. Included is a skin fixes this bug by decreasing the size of the pet shortcut bar horizontally; it also smooths the edges of your companion's skill icons by removing the dark pixels behind them. In addition to removing the empty skill slot, the draggable UI element is reduced in size and now lines up properly with the rest of your skill bars.

To apply this fix, relog into your character after activating the skin. By pasting the code from the SkinDefinition.xml file, you can also add this fix into other skin files.