fix(populate): make error reported when no localField specified catchable

Fix #6767

Author: vkarpov15

docs/source/api.js

@@ -104,9 +104,7 @@ function parse() {
         }
       }
 
-      if (ctx.string.includes('Model')) {
-        console.log(ctx);
-      }
+      console.log(ctx);
 
       // Backwards compat
       if (typeof ctx.constructor === 'string') {

lib/model.js

@@ -3946,7 +3946,7 @@ function getModelsMapForPopulate(model, docs, options) {
     }
 
     if (virtual && (!localField || !foreignField)) {
-      throw new Error('If you are populating a virtual, you must set the ' +
+      return new Error('If you are populating a virtual, you must set the ' +
         'localField and foreignField options');
     }
 

lib/query.js

@@ -1180,6 +1180,8 @@ Query.prototype.wtimeout = function wtimeout(ms) {
  *
  * Read more about how to use read concern [here](https://docs.mongodb.com/manual/reference/read-concern/).
  *
+ * @memberOf Query
+ * @method readConcern
  * @param {String} level one of the listed read concern level or their aliases
  * @see mongodb https://docs.mongodb.com/manual/reference/read-concern/
  * @return {Query} this