#309 Piechart remains after switching from resources to systems

[Jure Repinc]

Steps to reproduce
1. connected to demo2 which is running the RFTS ruleset
2. switched from systems to resources view
3. switched back to systems view

Actual result:
The piecharts were not cleared. Only systems were added on top of them.

Expected:
Piechart should be cleared and only systems should be shown.

[Jure Repinc]

Screenshot of the piechart bug.

[Jure Repinc]

Logged In: YES
user_id=126758
Originator: YES

Updated steps to reproduce:
1. connect to demo2 which is running the RFTS ruleset
2. set zoom to Fit
3. switch from systems to resources view
4. switch back to systems view
5. wait until the turn ends
6. update universe
7. set zoom to Fit
8. switch from systems to resources view
9. switch back to systems view

So it looks like you have to switch both times, before and after the tunr ends to see this. Don't know if it depends on setting zoom to Fit.