Make sure the security descriptor is initialized in RegGetKeySecurity.

dlls/advapi32/registry.c

diff --git a/dlls/advapi32/registry.c b/dlls/advapi32/registry.c
index 31f6815..b431234 100644
--- a/dlls/advapi32/registry.c
+++ b/dlls/advapi32/registry.c
@@ -1517,6 +1517,9 @@
     FIXME("(%x,%ld,%p,%ld): stub\n",hkey,SecurityInformation,
           pSecurityDescriptor,lpcbSecurityDescriptor?*lpcbSecurityDescriptor:0);
 
+    /* Do not leave security descriptor filled with garbage */
+    RtlCreateSecurityDescriptor(pSecurityDescriptor, SECURITY_DESCRIPTOR_REVISION);
+
     return ERROR_SUCCESS;
 }