fuzzing: Ensure input to g_uri_parse() is nul-terminated

The fuzzer will produce arbitrary binary blobs, which might not be
nul-terminated. `g_uri_parse()` has no length argument, so relies on
receiving a nul-terminated string as input. Guarantee that.

This should fix fuzzing build failures like
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=23750.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
14 jobs for uri-parsing-fix in 29 minutes and 42 seconds (queued for 13 seconds)
Status Job ID Name Coverage
  Style Check
passed #787683
check-todos

00:00:43

passed #787682
style-check-diff

00:01:10

 
  Build
passed #787688
cross-android_api21_arm64

00:04:14

passed #787689
cross-android_api28_arm64

00:01:27

passed #787690
cross-mingw64

00:06:02

passed #787685
debian-stable-x86_64

00:08:39

passed #787684
fedora-x86_64

00:13:35

passed #787687
G_DISABLE_ASSERT

00:06:12

passed #787686
installed-tests

00:10:38

passed #787691
win32-ps
msys2-mingw32

00:10:43

passed #787692
win32-ps
vs2017-x64

00:06:05

 
  Coverage
passed #787693
coverage

00:02:29

78.3%
 
  Analysis
passed #787695
scan-build

00:07:02

failed #787694
allowed to fail
valgrind

00:12:26

 
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=787694 responseStatus=201 Created token=xqfyDUqk
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=787694 responseStatus=201 Created token=xqfyDUqk
ERROR: Job failed: exit code 1