VLC does not show the previous frame after wake up

To reproduce on VLC[v3.2.0(334) on iPhone 6(iOS v12.4.1)]:

1. Start to play any video.
2. Wait few seconds and press pause button.
3. Press the Side button to put your iPhone to sleep.
4. Press the Side button once again for wake up and you can see blank screen rather previous frame, have a look please:

changed title from VLC does not show the last frame when video is on pause in some cases. to VLC does not show the previous frame after wake up

assigned to @bubu

changed milestone to %3.2.6

closed via merge request !108 (merged)

@bubu, thank you for not forgetting about this issue and fixing it.