Bug: Black frame on Mixer Keyer on new consumer

[MycroBeat]

Observed Behavior

Black frames are inserted and mixed when a new file is played if a keyer is actived.

Expected behaviour

Do a transparent fadeing using mask and a video.
When we do the step 4, the video that plays on layer 11 should fadeing out. When the animation is complete, before the d11e0f5 caspar will display the image mask (i think this shouldn't be normal, but it didn't cause any problems in the way i used it.). On 576a7b6 the animation fades very strangely and on top of that it also adds black frames in the first frames of the animation (in mix and out mix).

Steps to reproduce

1. MIXER 1-10 KEYER 1-11
2. PLAY 1-10 IMAGE_MASK.png
3. PLAY 1-11 VIDEO.mp4 MIX 10 LOOP
4. PLAY 1-11 EMPTY MIX 10

Environment

• Commit: 576a7b6
• Server version: 2.5 latest master
• Operating system: Windows 10 19044

[Julusian]

Caused by 895a5a0