Changes

Fix widget is disposed error during shutdown (#51)

After building a project and shuting down eclipse, the build console
will have a propertyChange event fired that will attempt to modify the
stream and background color that will trigger a use-after-dispose error
from SWT. This changeset ensures that the action is only taken on
non-disposed widgets.

Contributed by STMicroelectronics

Signed-off-by: Torbjörn Svensson <torbjorn.svensson@st.com>