Crashes on Mac when I set the gamma

[morshu9001]

I'm running OS X 10.10.3 (Yosemite). Sometimes, when I set the gamma with "/gamma 120", the game crashes. But this doesn't always happen. Sometimes, it works, but then the game crashes later when I re-open it later when it tries to set the gamma. And it tends to crash in waves. That is, it'll work fine for half a day then crash every time I set the gamma for hours at a different time. I don't see any pattern.
Does anyone else have this problem or a solution? I also have the latest version of the game. By the way, this never happened in AC 1.1.

(Edit) Here's the relevant error info:

Thread 0:: Dispatch queue: com.apple.main-thread
0 com.apple.CoreGraphics 0x9beac9e3 interpolate_table + 165
1 com.apple.CoreGraphics 0x9beac899 CGSGetDisplayTransferByTable + 249
2 SDL 0x001e7f8b SDL_SoftStretch + 21339
3 SDL 0x001cf40a SDL_GetGammaRamp + 186
4 SDL 0x001cf59c SDL_SetGammaRamp + 316
5 SDL 0x001cf850 SDL_SetGamma + 400
6 assaultcube 0x0005b883 0x1000 + 370819
7 assaultcube 0x0003e44c 0x1000 + 250956
8 assaultcube 0x0003f8b3 0x1000 + 256179
9 assaultcube 0x00048bfa 0x1000 + 293882
10 assaultcube 0x000483d7 0x1000 + 291799
11 assaultcube 0x000484a4 0x1000 + 292004
12 assaultcube 0x0005c5c5 0x1000 + 374213
13 assaultcube 0x0005df05 0x1000 + 380677
14 assaultcube 0x00002cbc 0x1000 + 7356