fixed FilteredSceneProcessor::acceptsInput() crash when inputPlug is null
fixed FilteredSceneProcessor::acceptsInput() crash when inputPlug is null

cedriclaunay/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,chippey/gaffer,andrewkaufman/gaffer,cedriclaunay/gaffer,goddardl/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,ivanimanishi/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,boberfly/gaffer,johnhaddon/gaffer,cedriclaunay/gaffer,andrewkaufman/gaffer,boberfly/gaffer,goddardl/gaffer,chippey/gaffer,lucienfostier/gaffer,chippey/gaffer,ImageEngine/gaffer,hradec/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,appleseedhq/gaffer,cedriclaunay/gaffer,chippey/gaffer,lucienfostier/gaffer,hradec/gaffer,lucienfostier/gaffer,boberfly/gaffer,ImageEngine/gaffer,goddardl/gaffer,ivanimanishi/gaffer,appleseedhq/gaffer,andrewkaufman/gaffer,boberfly/gaffer,appleseedhq/gaffer,hradec/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,hradec/gaffer,GafferHQ/gaffer,goddardl/gaffer,ivanimanishi/gaffer,hradec/gaffer