kernel32_winetest: format_msg test crashing silently

Created an attachment (id=7974)
debug log with windbg analysis, r56967

This issue has been regtested to rev. 56567: http://svn.reactos.org/svn/reactos/trunk/rostests/winetests/kernel32/format_msg.c?r1=53966&r2=56567&pathrev=56567
which adds null string arguments. Test exits prematurely, with possible exception:
(../../subsystems/win32/csrss/csrsrv/api/wapi.c:1221) Exception in 2d0.2d8. Killing...
(../../subsystems/win32/csrss/csrsrv/api/wapi.c:1114) Death from unknown thread, just continue
(../../subsystems/win32/csrss/csrsrv/api/wapi.c:1114) Death from unknown thread, just continue
format_msg.c:713: Test failed: failed out=?#?#3
format_msg.c:714: Test failed: failed: r=5

A debug session on msvc/windbg was performed, using revision 56967. Using +soe flag, 3 first-time exceptions can be caught, with 2nd and 3rd originating in kernel32_winetest!_gnu_exception_handler. 1st exception is attached, with analyze -v output.