Switched error message to loading message

Open a huge file (an image for instance) in the Text App and look at the `error` message.
I rather see a `Loading...` message instead.

What do you think?

![screenshot from 2013-12-23 14 59 44](https://f.cloud.github.com/assets/634478/1800989/a4e59514-6bda-11e3-9d87-18a86c4a4253.png)