winansi: check result before using Name for pty

[1480c1]

NtQueryObject under Wine can return a success but fill out no name.
In those situations, Wine will set Buffer to NULL, and set result to
the sizeof(OBJECT_NAME_INFORMATION).

Running a command such as

echo "$(git.exe --version 2>/dev/null)"

will crash due to a NULL pointer dereference when the code attempts to
null terminate the buffer, although, weirdly, removing the subshell or
redirecting stdout to a file will not trigger the crash.

Alternatives include checking Buffer itself, however, I am not sure
what is the official behavior of the function due to a lack of
documentation.
Another alternative is to check the Length field, but similar to above,
I do not know what the official behavior is.

This code is based on the behavior of NtQueryObject under wine and
reactos.

Signed-off-by: Christopher Degawa ccom@randomderp.com

opened gitgitgadget#1245 for now

[1480c1]

hmm, seems the second commit will be unneeded after #3864

[1480c1]

rebased on top of #3864 so CI can pass for now, please ignore the commits other than the last one

[dscho]

Thank you for working the Wine angle of Git for Windows!

[dscho]

Let's wait for the build to pass and then merge.