Fixed bug in ReactionEngine::removeReactor() - it now checks to see if the Reactor exists before calling isRunning() on it.
Fixed bug in ReactionEngine::removeReactor() - it now checks to see if the Reactor exists before calling isRunning() on it.

acmorrow/pion-core,acmorrow/pion-core,acmorrow/pion-core,acmorrow/pion-core,acmorrow/pion-core,acmorrow/pion-core,acmorrow/pion-core