Clicking Mark Origin on an Image Sprite without an Image generates an Internal Error

[jisqyv]

Describe the bug

If you click "Mark Origin" in the designer for an ImageSprite, which doesn't yet have an image set, you get the "Internal Error" message.

Affects

• [ x] Designer
• Blocks editor
• Projects Explorer
• Companion
• Compiled apps
• Buildserver
• Debugging
• Other... (please describe)

Expected behavior

An appropriate error message should be generated.

Steps to reproduce

Create a new project, drag in a Canvas and place an Image Sprite in it (but don't set an image). Then click "Mark Origin" on the Image Sprite.

[ewpatton]

Fixed by #3195