Fix two issues related to 'partial' .blend files:
authorBastien Montagne <montagne29@wanadoo.fr>
Wed, 14 Sep 2016 09:35:16 +0000 (11:35 +0200)
committerSergey Sharybin <sergey.vfx@gmail.com>
Wed, 14 Sep 2016 09:41:16 +0000 (11:41 +0200)
commit9a35ebc1ea81792747b9037239f4e9b0c377edd8
treeecdbb53e202303ecce00b0122c709619595cc99d
parentdf4602ee3bfa33a481fede6cfee64d9819a1a3dd
Fix two issues related to 'partial' .blend files:

I) Filename was not put in temp Main generated to save selected data only,
this was breaking readcode when trying to open partial file, leading to missing
filename in final loaded Main data.

II) Read code would confuse partial .blend files with Undo ones, when they had no screen in them
(which happens to 99.999% of partial .blend files I guess).

Reported by @sybren, thanks.

Should be safe enough for 2.78 release.
source/blender/blenkernel/intern/blendfile.c