Prevent error when removing a model that does not match a view (#3472)

Resolves #3445

If using `buildChildView` to build views that aren't given the collection's model, when the model is removed it would throw errors when other methods expected views to exist.

src/next-collection-view.js

@@ -131,13 +131,19 @@ const CollectionView = Backbone.View.extend({
   },
 
   _removeChildModels(models) {
-    return _.map(models, _.bind(this._removeChildModel, this));
+    return _.reduce(models, (views, model) => {
+      const removeView = this._removeChildModel(model);
+
+      if (removeView) { views.push(removeView); }
+
+      return views;
+    }, []);
   },
 
   _removeChildModel(model) {
     const view = this.children.findByModel(model);
 
-    this._removeChild(view);
+    if (view) { this._removeChild(view); }
 
     return view;
   },

test/unit/next-collection-view/collection-view-data.spec.js

@@ -251,4 +251,26 @@ describe('next CollectionView Data', function() {
       expect(myCollectionView.$el.children()).to.have.lengthOf(2);
     });
   });
+
+  describe('when removing a model that does not match a children view model', function() {
+    let myCollectionView;
+    let collection;
+
+    beforeEach(function() {
+      collection = new Backbone.Collection([{ id: 1 }, { id: 2 }, { id: 3 }]);
+
+      const BuildCollectionView = MyCollectionView.extend({
+        buildChildView(child, ChildViewClass) {
+          return new ChildViewClass({ model: new Backbone.Model() });
+        }
+      });
+
+      myCollectionView = new BuildCollectionView({ collection });
+      myCollectionView.render();
+    });
+
+    it('should not throw an error', function() {
+      expect(collection.remove({ id: 1 })).to.not.throw;
+    });
+  });
 });