rlc_um_nr_test: add extra check to verify reassembly timer isn't running

lib/test/rlc/rlc_um_nr_test.cc

@@ -552,7 +552,7 @@ int rlc_um_nr_test8()
   return SRSRAN_SUCCESS;
 }
 
-// Similar to rlc_um_nr_test9() but out-of-order PDUs have SNs (from multiple SDUs)
+// Similar to rlc_um_nr_test8() but out-of-order PDUs have SNs (from multiple SDUs)
 int rlc_um_nr_test9()
 {
   rlc_um_nr_test_context1 ctxt;
@@ -612,6 +612,8 @@ int rlc_um_nr_test9()
     TESTASSERT(*(ctxt.tester.sdus[i]->msg) == i);
   }
 
+  TESTASSERT(ctxt.timers.nof_running_timers() == 0);
+
   return SRSRAN_SUCCESS;
 }