Please describe the problem:
As I enter a space into the text file. The text file changes content-type for an unknown unexplainable reason and hence changes default launching software as well. In this case to Grapviz dot.

Steps to reproduce:
1. Enter into gedit, "Automatically add <p> </p> aruond paragraphs of text, unless the paragraph"
2. Save
3. Add a space and save(it is now detected as a Graphviz dot file)


Actual results:
First when the file is saved it is detected as text
After adding a space to the end of the line it is however detected as Graphviz dot

Expected results:
Keep being detected as a text file.

Does this happen every time?
Yes

Other information:
http://launchpadlibrarian.net/28490754/Screenshot-1.png
http://launchpadlibrarian.net/28490767/Screenshot-2.png