[Minor] Force actions: deal with null better

diff --git a/src/plugins/lua/force_actions.lua b/src/plugins/lua/force_actions.lua
index 6c01afc2b511d991bd227cba01205becbfc07f6c..e5c309c2423726c05cc2da7a4c7a29df1f19a7a9 100644 (file)
--- a/src/plugins/lua/force_actions.lua
+++ b/src/plugins/lua/force_actions.lua
@@ -57,7 +57,7 @@ local function gen_cb(expr, act, pool, message, subject)
       if subject then
         task:set_metric_subject(subject)
       end
-      if message then
+      if type(message) == 'string' then
         task:set_pre_result(act, message)
       else
         task:set_pre_result(act)