Optimization: disable rule if variables are empty

rootfs/etc/knot-resolver/knot-aliases-alt.conf

@@ -1,4 +1,4 @@
 -- Dummy file. Filled by antizapret script.
 blocked_hosts = {}
-regex_blocked = '^$'
-regex_allowed = '^$'
+regex_blocked = ''
+regex_allowed = ''

rootfs/etc/knot-resolver/kresd.conf

@@ -48,32 +48,30 @@ local adguard = os.getenv('ADGUARD')
 -- if not dns then dns = '127.0.0.11' end
 -- if not dns_ru then dns = '77.88.8.8' end
 
-policy.add(
-    function (_, query)
-        if (regex_allowed == '' or regex_allowed == nil) and (regex_blocked  == '' or regex_blocked == nil) then
-            return nil
-        end
+if (regex_allowed ~= '' or regex_blocked  ~= '') then
+    policy.add(
+        function (_, query)
+            local command = string.format(
+                '/etc/knot-resolver/regex.sh "%s" "%s" "%s"',
+                kres.dname2str(query.sname),
+                regex_allowed,
+                regex_blocked
+            )
+            local handle = io.popen(command)
+            local result = handle:read("*line")
+            handle:close()
 
-        local command = string.format(
-            '/etc/knot-resolver/regex.sh "%s" "%s" "%s"',
-            kres.dname2str(query.sname),
-            regex_allowed,
-            regex_blocked
-        )
-        local handle = io.popen(command)
-        local result = handle:read("*line")
-        handle:close()
-
-        if result == 'blocked' then
-            return policy.STUB({'127.0.0.4'})
-        elseif result == 'allowed' then
-            return policy.FORWARD({dns})
-        end
+            if result == 'blocked' then
+                return policy.STUB({'127.0.0.4'})
+            elseif result == 'allowed' then
+                return policy.FORWARD({dns})
+            end
 
-        -- filter did not match, continue with next filter
-        return nil
-    end
-)
+            -- filter did not match, continue with next filter
+            return nil
+        end
+    )
+end
 
 -- Forward blocked domains to dnsmap
 policy.add(