[ntdll] Care about empty fields of assembly_identity structure in actctx.c

[Roman Mindalev]

Jacek Caban wrote:
> Hi Roman,
> 
>> On parsing of manifest in PE module is possible access to zero address
>> and crash. It's happens because not all manifest attributes can be
>> specified and pointers in assembly_identity structure can be
>> uninitialized. This patch adds function for setting empty strings in
>> structure elements when they not initialized.
> 
> 
> Your patch looks like a workaround. You should fix the code to cope with 
> NULL pointers correctly instead of allocating useless empty strings.
> Also initialize_assembly_identity doesn't make sense. ai is initialized 
> a few lines later by memset call.

Thanks for your notices!
I'm rewrote patch, append some changes and split to small parts.