Color changes with keys don't show up with "vector as raster"

[Al532]

Describe the bug
Color changes via keys in the level palette don't show up in the viewer when "visualise vector as raster" is toggled (however it does show up in preview mode).

To Reproduce
List steps to reproduce the behavior.

1. Toggle the "visualise vector as raster" option
2. Create a vector layer
3. Fill a rectangle with a random color style, and expose it from frame 1 to 10
4. Set a palette key at frame 1
5. Set a palette key at frame 10
6. At frame 10, change parameters of the color style (as alpha, R, G, B...)

Expected behavior
If you browse (or playback) from frames 1 to 10, no color change appear (despite the parameters of the color style do change in the level palette view). The color displayed corresponds to the last key set. If you uncheck "vector as raster", it shows up as it is suppose to.

Device Information:

• OS: Windows 8.1
• OpenToonz Version: 1.4
• GPU: NVIDIA GTX 660
• GPU Driver Version: 445.87