Don't allow the user to set the 'ID' of exported canvases to be empty.
-rw-r--r-- 3741 .gitignore
-rw-r--r-- 1453 .valgrind
drwxr-xr-x - ETL
drwxr-xr-x - autobuild
drwxr-xr-x - gtkmm-osx
drwxr-xr-x - synfig-core
drwxr-xr-x - synfig-docs
drwxr-xr-x - synfig-osx
drwxr-xr-x - synfig-studio