Image instances lose their 'filename' property after calling .show()

[nicovillanueva]

Version: 1.3 Environment: Linux Mint 17 Interpreter: Python 2.7.6

Steps:

1. Create a new Image instance
2. Get the 'filename' property of the instance (not necessary, but to ensure that it works)
3. Call .show() on the instance
4. Repeat step 2: The filename will be None

Screenshot: