Add some asserts into the common demo tasks to catch scenarios where the tasks are...

Add some asserts into the common demo tasks to catch scenarios where the tasks are not being used but the part of the demo/test that gets called from the tick hook is called resultant in an access to objects that were not created.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2746 1d2547de-c912-0410-9cb9-b8ca96c0e9e2