[fixed] Preview+map gone on user tracks

[Wuzzy]

There is a small bug which causes the preview image and map to disappear in the track submenu.

Steps to reproduce:

1. Open the quick race menu
2. Select any non-official track
3. Open the challenge menu
4. Select any challenge
5. Select the “track” tab
6. Click on “<” or “>”

Expected result: You see a description of a challenge track along with track data, a preview image and a map.
Actual result: You see a description of a challenge track along with track data, no preview image and no map.

Fun fact: If you select an official track in the quick race menu again and repeat steps 2 to 6, you get the expected result.

• Stunt Rally 2.2.1
• Linux 3.12.7
• NVIDIA driver 331.38