Remove null pointer exception because of complex to string method

solutions/RSync/src/main/scala/MainApp.scala

@@ -67,7 +67,7 @@ object MainApp extends App {
     CompleteTTCProcess.validateModelEquality()
 
     /*if (CompleteTTCProcess.sync) {
-      CompleteTTCProcess.showSyncFunctionalityAtExample()
+      CompleteTTCProcess.showSyncFunctionalityByExample()
     }*/
   })
 

solutions/RSync/src/main/scala/sync/bdd/Assignment.scala

@@ -32,7 +32,7 @@ class Assignment(protected var value: Boolean, protected var owner: Leaf, protec
   }
 
   override def toString(): String = {
-    "Assignment:" + " port=" + port.getName() + " value=" + value
+    "Assignment:" + " port=" + port + " value=" + value
   }
 
 }

solutions/RSync/src/main/scala/ttc2019/CompleteTTCProcess.scala

@@ -97,7 +97,7 @@ object CompleteTTCProcess extends App {
   /**
    * Show how to incrementally remove a row and add a new row with output.
    */
-  def showSyncFunctionalityAtExample(): Unit = {
+  def showSyncFunctionalityByExample(): Unit = {
     ModelElementLists.printFromPackage("sync.bdd.BDD")
 
     val row = ModelElementLists.getElementFromType("sync.tt.Row").asInstanceOf[Row]
@@ -148,7 +148,7 @@ object CompleteTTCProcess extends App {
   override def main(args: Array[String]): Unit = {
     val processConfig = TTCProcessConfiguration(ttFileName = "TT.ttmodel", bddFileName = "Generated.bddmodel", processMode = ProcessMode.SYNC)
     executeEntireProcess(processConfig)
-    showSyncFunctionalityAtExample()
+    showSyncFunctionalityByExample()
   }
 
 }