2013-12-09 Igor Oliveira <igor.o@sisa.samsung.com>
        Fix WebCLObject::releasePlatformObject
        Issue #373

        Reviewed by Antonio.

        releasePlatformObject needs to verify if platformObject is valid
        before calling releasePlatformObjectImpl.

        * Modules/webcl/WebCLEvent.cpp:
        (WebCore::WebCLEvent::releasePlatformObjectImpl):
        * Modules/webcl/WebCLObject.h:
        (WebCore::WebCLObjectImpl::releasePlatformObject):