Add a missing check to g_utf8_get_char_validated()

g_utf8_get_char_validated() was not exactly matching its
documentation. The function was not checking if the sequence of
unicode characters was free of null bytes before performing a more
in-depth validation.

Fix issue #1052
13 jobs for g_utf8_get_char_validated_wrong_return_on_null_byte in 42 minutes and 36 seconds (queued for 2 minutes and 52 seconds)
Status Job ID Name Coverage
  Build
passed #432639
cross-android_api21_arm64

00:02:53

passed #432640
cross-android_api28_arm64

00:02:46

passed #432641
cross-mingw64

00:04:15

passed #432637
debian-stable-x86_64

00:06:42

passed #432694
fedora-x86_64

00:09:06

passed #432693
G_DISABLE_ASSERT

00:03:26

passed #432642
win32
msys2-mingw32

00:08:30

passed #432643
win32
vs2017-x64

00:09:19

failed #432636
fedora-x86_64

00:06:57

failed #432638
G_DISABLE_ASSERT

00:06:26

 
  Coverage
passed #432644
coverage

00:01:43

77.9%
 
  Analysis
passed #432646
scan-build

00:05:45

failed #432645
allowed to fail
valgrind

00:12:14

 
Name Stage Failure
failed
valgrind Analysis
Uploading artifacts...
_build/config.h: found 1 matching files
_build/glib/glibconfig.h: found 1 matching files

_build/meson-logs: found 7 matching files

Uploading artifacts to coordinator... ok
id=432645 responseStatus=201 Created token=Egt3xtR3
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=432645 responseStatus=201 Created token=Egt3xtR3
ERROR: Job failed: exit code 1