Annotation Tools: Thumbnail check breaks tool on creation

**Affected Courses:**  3 courses are affected (Visualizing Japan, ChinaX, HeroesX) with a total enrollment of ~35,000 students.
**Ideal Fix Deployment:** Ideally, today. Otherwise as soon as possible. 

**Background:** After the code release earlier today (9/25) I received messages from course instructors and students that they could not make image annotations. Checking the console I noticed the issue was caused by the bug fix I made that was released earlier today. During testing I had neglected to realize that the code actually broke annotation creation. No annotations can be created due to "thumbnails" being saved only after a user hits "Save" instead of before. 

**Studio Changes:** None.

**LMS Changes:** Users should now be able to create annotations

**Testing:**
1. Install the [tarball](https://www.dropbox.com/s/r684ber7z4ddqtc/2014_T4.DPRfFs.tar.gz) as usual.
2. Try to make an annotation. It failed on creation before. Now it does not. 
    a. The previous error was an AttributeError trying to find "thumb" of undefined, which is because the function runs on annotations that have not yet been saved. "thumb" is attached only during the saving process. This mitigates that.