Issue #38: Exception thrown when validating a communication pattern

src/tmltranslator/HwCrossbar.java

src/tmltranslator/HwDMA.java

src/tmltranslator/HwExecutionNode.java

src/tmltranslator/HwLink.java

src/tmltranslator/HwVGMN.java

src/tmltranslator/TMLActivity.java

src/tmltranslator/TMLActivityElement.java

src/tmltranslator/TMLActivityElementChannel.java

src/tmltranslator/TMLActivityElementEvent.java

src/tmltranslator/TMLAttribute.java

src/tmltranslator/TMLCP.java

src/tmltranslator/TMLCPLibArtifact.java

src/tmltranslator/TMLCPSyntaxChecking.java

src/tmltranslator/TMLCPTextSpecification.java

src/tmltranslator/TMLChoice.java

src/tmltranslator/TMLCommunicationElement.java

src/tmltranslator/TMLEvent.java

src/tmltranslator/TMLModeling.java

src/tmltranslator/TMLPort.java

src/tmltranslator/TMLRandomSequence.java