remove redundant picture initialization

These values are already set in picture_alloc_with_edges().
14 jobs for seq_hdr_allocator/1 in 5 minutes and 15 seconds (queued for 1 second)
Status Job ID Name Coverage
  Style
passed #246894
amd64 debian
style-check

00:00:20

 
  Build
passed #246895
amd64 debian
build-debian

00:00:36

passed #246900
debian aarch64
build-debian-aarch64

00:01:29

passed #246901
debian aarch64
build-debian-aarch64-clang-5

00:01:09

passed #246896
amd64 debian
build-debian-static

00:00:33

passed #246903
debian aarch64
build-debian-werror

00:00:34

passed #246897
amd64 debian
build-debian32

00:00:25

passed #246902
macos
build-macos

00:00:27

passed #246898
win32
build-win32

00:00:31

passed #246899
win64
build-win64

00:00:34

 
  Test
passed #246904
amd64 debian
test-debian

00:00:47

passed #246905
amd64 debian
test-debian-asan

00:02:03

passed #246906
amd64 debian
test-debian-msan

00:01:01

passed #246907
amd64 debian
test-debian-ubsan

00:01:20