GWin32RegistryKey: Move assertions

While these assertions look right at the first glance,
they actually crash the program. That's because GObject
insists on initializing all construct-only properties
to their default values, which results in
g_win32_registry_key_set_property() being called multiple
times with NULL string, once for each unset property.

If "path" is actually set by the caller, a subsequent
call to set "path-utf16" to NULL will fail an assertion,
since absolute_path is already non-NULL.

With assertions moved the set-to-NULL calls bail out before
an assertion is made.
14 jobs for backport-1517-win32-registry-assertions in 64 minutes and 24 seconds
Status Job ID Name Coverage
  Style Check
passed #754144
check-todos

00:01:06

failed #754143
allowed to fail
style-check-diff

00:00:51

 
  Build
passed #754149
cross-android_api21_arm64

00:01:21

passed #754150
cross-android_api28_arm64

00:03:53

passed #754151
cross-mingw64

00:04:49

passed #754146
debian-stable-x86_64

00:08:38

passed #754145
fedora-x86_64

00:19:49

passed #754148
G_DISABLE_ASSERT

00:10:10

passed #754147
installed-tests

00:05:04

passed #754152
win32-ps
msys2-mingw32

00:11:21

passed #754153
win32-ps
vs2017-x64

00:08:05

 
  Coverage
passed #754154
coverage

00:01:28

78.2%
 
  Analysis
passed #754156
scan-build

00:41:57

failed #754155
allowed to fail
valgrind

00:37:32

 
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=754155 responseStatus=201 Created token=-Sj_GX38
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=754155 responseStatus=201 Created token=-Sj_GX38
ERROR: Job failed: exit code 1
failed
style-check-diff Style Check
 #        ifdef DLL_EXPORT
-# define GOBJECT_VAR extern __declspec(dllexport)
+#define GOBJECT_VAR extern __declspec(dllexport)
# else /* !DLL_EXPORT */
# define GOBJECT_VAR extern
# endif /* !DLL_EXPORT */
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1