JBIDE-17471 JBIDE-17463 : fix various NPE & disposed widget issues

Signed-off-by: Fred Bricon <fbricon@gmail.com>
JBDS-3050 - An internal error occurred during: 'Computing size'. The profile is currently in use.
JBIDE-17412 : ensure org.jboss.tools.project.examples.projectExamplesXml extension points without urlKey don't break

Signed-off-by: Fred Bricon <fbricon@gmail.com>