fix seqstat merge summary

public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/tools/SeqStat.scala

@@ -60,6 +60,7 @@ class SeqStat(val root: Configurable) extends ToolCommandFuntion with Summarizab
       case (v1: Int, v2: Int) if key == "len_min" => if (v1 < v2) v1 else v2
       case (v1: Int, v2: Int) if key == "len_max" => if (v1 > v2) v1 else v2
       case (v1: Int, v2: Int)                     => v1 + v2
+      case (v1: Long, v2: Long)                   => v1 + v2
       case _                                      => v1
     }
   }