Loads blank project whenever project file is opened from within file manager

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create a project with something in it (a text label, box, line, combobox 
etc.)
2. Save the project in a folder where user has read and write access (on Linux 
usually in user's /home folder)
3. Open Xfce's filemanager Thunar, choose the project file and using the 
context menu select "Open with Pencil" (if not present, choose "Open With->Open 
With Other Application")

Expected output:
Project that was saved previously

Output:
Blank project - single untitled document with a single empty untitled page

System:
Debian 7 Wheezy 64bit up-to-date with Xfce 4 as desktop environment
Evolus Pencil 2.0.5

Additional information:
Opening the file using pencil command in terminal + file itself produces the 
same result. However when inside Pencil using the main menu "File->Open" 
project loads as expected. At first I thought that project is simply not stored 
properly. However the file that was created increased in size whenever I stored 
the current state after adding some new elements. Also opening the project file 
with a simple text editor revealed to me that the content is indeed there.

Original issue reported on code.google.com by redbaron...@gmail.com on 2 Dec 2014 at 1:43

[GoogleCodeExporter]

I have also discovered that "Open recent" from the main menu produces the exact 
same buggy result, which leads me to believe that the problem is indeed not 
coming from Thunar but from Pencil itself since "Open recent" is withing the 
application's own environment.

Original comment by redbaron...@gmail.com on 2 Dec 2014 at 9:36