fix big memory leak in E1 TS2 handling

diff --git a/src/misdn.c b/src/misdn.c
index a8e5dca..e4d9202 100644
--- a/src/misdn.c
+++ b/src/misdn.c
@@ -300,6 +300,9 @@
 		DEBUGP(DMIB, "got unexpected 0x%x prim\n", hh->prim);
 		break;
 	}
+	/* FIXME: don't free it if we still hold reference! */
+	msgb_free(msg);
+
 	return ret;
 }