[0.4.x] Segfault in function blit_overlay_noalpha (lv_video.c)

[hartwork]

Hi! 👋

I ran into this segfault two days ago. I'm not sure how to reproduce it yet. AddressSanitizer said this:

[..]
Switching to actor 'corona'...
AddressSanitizer:DEADLYSIGNAL
=================================================================
==102688==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7fa865f216d2 bp 0x7ffef8062710 sp 0x7ffef8062700 T0)
==102688==The signal is caused by a WRITE memory access.
==102688==Hint: address points to the zero page.
    #0 0x7fa865f216d2 in mem_copy_c [..]/libvisual/libvisual/libvisual/lv_mem.c:203
    #1 0x7fa865f137c6 in blit_overlay_noalpha [..]/libvisual/libvisual/libvisual/lv_video.c:1288
    #2 0x7fa865f1c0b1 in visual_video_blit_overlay_custom [..]/libvisual/libvisual/libvisual/lv_video.c:1259
    #3 0x7fa865f1c4b1 in visual_video_blit_overlay [..]/libvisual/libvisual/libvisual/lv_video.c:1177
    #4 0x7fa865f07cef in visual_actor_run [..]/libvisual/libvisual/libvisual/lv_actor.c:775
    #5 0x7fa865f0da6c in visual_bin_run [..]/libvisual/libvisual/libvisual/lv_bin.c:867
    #6 0x55f828f281ee in LV::Bin::run() [..]/libvisual/libvisual/tools/lv-tool/lv-tool.cpp:111
    #7 0x55f828f281ee in main [..]/libvisual/libvisual/tools/lv-tool/lv-tool.cpp:869
    #8 0x7fa865b41d09 in __libc_start_main ../csu/libc-start.c:308
    #9 0x55f828f25889 in _start ([..]/libvisual/INSTALL_PREFIX/bin/lv-tool+0x5889)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV [..]/libvisual/libvisual/libvisual/lv_mem.c:203 in mem_copy_c
==102688==ABORTING

Any help with reproducing and/or fixing this issue is welcome!

Thanks and best, Sebastian