NullSumException

//Submitted by Dima Yankovoy 311868442 & Snir Yacoby 201561933
package il.ac.hit.project.model

/**
 * NullSumException is thrown when the method convert() cannot proceed - the sum that it gets is either 0
 * or a negative number.
 * @param msg The message thrown with description of the exception.
 * @param cause The possible cause for the exception.
 */
class NullSumException(msg: String = null, cause : Throwable = null ) extends Exception(msg, cause){

  def this() = this("",null)
  def this(msg: String ) = this(msg,null)
  def this(cause: Throwable) = this("", cause)
}