Optional field code generation bug fix see !813 and HQ51693

Enables to assign Optional<Type> to Type
Signed-off-by: Adam Knapp <adam.knapp@ericsson.com>

org.eclipse.titan.designer/src/org/eclipse/titan/designer/AST/TTCN3/values/Referenced_Value.java

@@ -686,7 +686,6 @@ public final class Referenced_Value extends Value {
 
 		final ExpressionStruct expression = new ExpressionStruct();
 		reference.generateConstRef(aData, expression);
-		generateCodeExpressionOptionalFieldReference(aData, expression, reference);
 
 		return expression.expression;
 	}

org.eclipse.titan.runtime/src/org/eclipse/titan/runtime/core/Base_Type.java

@@ -254,6 +254,16 @@ public abstract class Base_Type {
 	 */
 	public abstract Base_Type operator_assign(final Base_Type otherValue);
 
+	/**
+	 * Assigns the other optional value to this value.
+	 * 
+	 * @param otherValue the other value to assign.
+	 * @return the new value object.
+	 */
+	public Base_Type operator_assign(final Optional<?> otherValue) {
+		return operator_assign(otherValue.constGet());
+	}
+
 	/**
 	 * Logs this value.
 	 */