Exception in test window (from sort directories change)

[dangoor]

This does not cause a failure, but there is an exception in the spec runner window:

Exception when calling a 'brackets done loading' handler: AppInit.js:61
TypeError: Cannot read property 'fullPath' of null
    at _refreshFileTreeInternal (file:///Applications/Brackets.app/Contents/dev/src/project/ProjectManager.js:1285:38)
    at refreshFileTree (file:///Applications/Brackets.app/Contents/dev/src/project/ProjectManager.js:1334:43)
    at Preference.<anonymous> (file:///Applications/Brackets.app/Contents/dev/src/project/ProjectManager.js:2211:9)
    at Preference.o.event.dispatch (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:3:6055)
    at Preference.r.handle (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:3:2830)
    at Object.o.event.trigger (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:3:5163)
    at Preference.<anonymous> (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:3:11000)
    at Function.o.extend.each (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:2:2877)
    at o.fn.o.each (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:2:818)
    at o.fn.extend.trigger (file:///Applications/Brackets.app/Contents/dev/src/thirdparty/jquery-2.1.0.min.js:3:10976) AppInit.js:62

This was introduced in 34db31a. It looks like the ProjectManager is trying to sort things before there is a project open. A simple fix is to put in a check to make sure that the value of the pref actually changed. I'll put up a pull request for that.

cc @TomMalbran