Illusioner acts like casting spell even if he is not applying blindness

The bug

Since 17w17a illusioners will not always apply blindness to nearby players, they will however still act like they are casting a spell.

Expected would be that they do not act like they are casting a spell if they do not apply blindness.

How to reproduce

1. Set difficulty to "Easy" or "Normal"
2. Spawn an illusioner
   It acts like casting a spell, but nothing happens