Resolve "Fix the rulehandler to avoid running rules twice inside the `eval` function"

Closes #20 (closed)

\approve @ds @laurens @chengzhi

rulelib/rulehandler.py

@@ -129,8 +129,9 @@ class RuleHandler:
             if rule.db_name is not None:
                 args["database"] = self.databases[rule.db_name]
 
-            if rule(**args) is not None:
-                args.update(rule(**args))
+            rule_result = rule(**args)
+            if rule_result is not None:
+                args.update(rule_result)
 
         # Close all database connections.
         for database in self.databases.values():