fix(core): support null handler

packages/core/lib/register.js

@@ -3,9 +3,7 @@ import registry from "@nikitajs/core/registry";
 
 // Action registration
 const actions = {
-  "": {
-    handler: function () {},
-  },
+  "": {},
   assert: "@nikitajs/core/actions/assert",
   call: "@nikitajs/core/actions/call",
   execute: {

packages/core/lib/session.js

@@ -178,7 +178,7 @@ const session = function(args, options = {}) {
       hooks: action.hooks.on_action, //  || action.hooks.["nikita:action"]
       handler: function(action) {
         // Execution of an action handler
-        return action.handler.call(action.context, action);
+        return action.handler?.call(action.context, action);
       }
     });
     // Ensure child actions are executed even after parent execution

packages/core/test/actions/call.coffee

@@ -21,6 +21,25 @@ describe 'actions.call', ->
         registry.unregister 'my_function'
 
   describe 'external module', ->
+
+    they 'doesnt support plain declaration', ({ssh}) ->
+      # The problem has found a solution to support `metadata.module`
+      # Setting `metadata.module` conflict with the already defined value
+      # setup by `registry#load`.
+      # When argument is not defined (eg not a string, mapped to the handler),
+      # mapping the metadata.module create a infinite loop
+      # where `nikita.call` is importing itself
+      nikita
+        $ssh: ssh
+        $tmpdir: true
+      , ({metadata: {tmpdir}}) ->
+        result = await nikita.call
+          $:
+            metadata:
+              module: "#{tmpdir}/my_module.js"
+            config:
+              my_key: 'my value'
+        result.should.not.containEql my_key: 'my value'
 
     they 'defined as a function', ({ssh}) ->
       nikita