Fix multiple render of mj attributes

Author: iRyusa

packages/mjml-core/src/mjCssClasses.js

@@ -1,11 +1,13 @@
-let mjCssClasses = {}
+import _map from "lodash/map"
+
+const mjCssClasses = {}
 
 export const setMjCssClasses = (mjClass, attributes) => {
   mjCssClasses[mjClass] = attributes
 }
 
 export const resetCssClasses = () => {
-  mjCssClasses = {}
+  _map(mjCssClasses, (v, k) => delete mjCssClasses[k])
 }
 
 export default mjCssClasses

packages/mjml-core/src/mjDefaultAttributes.js

@@ -1,11 +1,13 @@
-let mjDefaultAttributes = {}
+import _map from "lodash/map"
+
+const mjDefaultAttributes = {}
 
 export const setMjDefaultAttributes = (tagName, attributes) => {
   mjDefaultAttributes[tagName] = attributes
 }
 
 export const resetDefaultAttributes = () => {
-  mjDefaultAttributes = {}
+  _map(mjDefaultAttributes, (v, k) => delete mjDefaultAttributes[k])
 }
 
 export default mjDefaultAttributes