Treemap chart throws errors during series drill down, while styled mode is enabled.

[Denyllon]

Expected behaviour

Correct drilling down to all series levels.

Actual behaviour

After drilling down to first level, there is Uncaught TypeError: Cannot read property 'css' of null throwed in the console, and there is no possibility to drill down deeper into the next series level.

Live demo with steps to reproduce

http://jsfiddle.net/daniel_s/uprqt7yn/

1. Click on any of series
2. Open console (there is an error), and isn't possible to drill down deeper.

Occurency

v5.0.13 and above