[Minor] Avoid `nil` table

rules/misc.lua

@@ -578,6 +578,7 @@ rspamd_config.INFO_TO_INFO_LU = {
       return false
     end
     local to = task:get_recipients('smtp')
+    if not to then return false end
     local found = false
     for _,r in ipairs(to) do
       if util.strequal_caseless(r['user'], 'info') then
@@ -609,4 +610,4 @@ rspamd_config.R_BAD_CTE_7BIT = {
   score = 4.0,
   description = 'Detects bad content-transfer-encoding for text parts',
   group = 'header'
-}
+}