Update curPath for nested path

Author: csy1204

lib/helpers/populate/assignVals.js

@@ -144,7 +144,7 @@ module.exports = function assignVals(o) {
 
     const parts = _path.split('.');
     let cur = docs[i];
-    const curPath = parts[0];
+    let curPath = parts[0];
     for (let j = 0; j < parts.length - 1; ++j) {
       // If we get to an array with a dotted path, like `arr.foo`, don't set
       // `foo` on the array.
@@ -167,6 +167,7 @@ module.exports = function assignVals(o) {
         cur[parts[j]] = {};
       }
       cur = cur[parts[j]];
+      curPath += parts[j + 1] ? `.${parts[j + 1]}` : '';
       // If the property in MongoDB is a primitive, we won't be able to populate
       // the nested path, so skip it. See gh-7545
       if (typeof cur !== 'object') {