Fix T85395: Texture paint external edit wrong projection on reapply

Caused by rB5b34d11b55e0.

Above commit restored the view matrices in ED_view3d_draw_offscreen
_before_ they can be stored in the ImBuff (see ED_view3d_draw_offscreen
/ texture_paint_image_from_view_exec).

Now make restoring the view matrices optional and dont do this in case
of reprojection, so the used matrices can still be saved in the ImBuff
later.

Reviewed By: campbellbarton

Maniphest Tasks: T85395

Differential Revision: https://developer.blender.org/D10331

source/blender/windowmanager/intern/wm_files.c

@@ -1363,6 +1363,7 @@ static ImBuf *blend_file_thumb(const bContext *C,
                                           IB_rect,
                                           R_ALPHAPREMUL,
                                           NULL,
+                                          true,
                                           NULL,
                                           err_out);
   }