fix undo removes cursor preview

src/containers/blob/blob.js

@@ -4,6 +4,7 @@ import BroadBrushHelper from './broad-brush-helper';
 import SegmentBrushHelper from './segment-brush-helper';
 import {MIXED, styleCursorPreview} from '../../helper/style-path';
 import {clearSelection} from '../../helper/selection';
+import {getGuideLayer} from '../../helper/layer';
 
 /**
  * Shared code for the brush and eraser mode. Adds functions on the paper tool object
@@ -166,7 +167,7 @@ class Blobbiness {
             this.cursorPreviewLastPoint = point;
         }
 
-        if (this.cursorPreview &&
+        if (this.cursorPreview && this.cursorPreview.parent &&
                 this.brushSize === this.options.brushSize &&
                 this.fillColor === this.options.fillColor &&
                 this.strokeColor === this.options.strokeColor) {
@@ -176,6 +177,8 @@ class Blobbiness {
             center: point,
             radius: this.options.brushSize / 2
         });
+        newPreview.parent = getGuideLayer();
+        newPreview.data.isHelperItem = true;
         if (this.cursorPreview) {
             this.cursorPreview.remove();
         }

src/containers/line-mode.jsx

@@ -4,7 +4,6 @@ import React from 'react';
 import {connect} from 'react-redux';
 import bindAll from 'lodash.bindall';
 import Modes from '../modes/modes';
-import {changeStrokeWidth} from '../reducers/stroke-width';
 import {clearSelection, getSelectedLeafItems} from '../helper/selection';
 import {MIXED} from '../helper/style-path';
 import {changeMode} from '../reducers/modes';

src/helper/selection.js

@@ -178,7 +178,6 @@ const _deleteItemSelection = function (items, onUpdateSvg) {
 };
 
 const _removeSelectedSegments = function (items, onUpdateSvg) {
-    performSnapshot(undoSnapshot);
     const segmentsToRemove = [];
     
     for (let i = 0; i < items.length; i++) {

src/helper/undo.js

@@ -12,6 +12,9 @@ const performSnapshot = function (dispatchPerformSnapshot) {
 };
 
 const _restore = function (entry, onUpdateSvg) {
+    for (const layer of paper.project.layers) {
+        layer.removeChildren();
+    }
     paper.project.clear();
     paper.project.importJSON(entry.json);
     paper.view.update();