fix issue with undo because this.elem was overwritten with node.remove()

cypress/integration/ui/issues/issue-359.js

@@ -0,0 +1,26 @@
+import {
+  visitAndApproveStorage
+} from '../../../support/ui-test-helper.js';
+
+// See https://github.com/SVG-Edit/svgedit/issues/359
+describe('Fix issue 359', function () {
+  beforeEach(() => {
+    visitAndApproveStorage();
+  });
+
+  it('can undo without throwing', function () {
+    cy.get('#tool_source').click();
+    cy.get('#svg_source_textarea')
+      .type('{selectall}')
+      .type(`<svg width="640" height="480" xmlns="http://www.w3.org/2000/svg">
+      <g class="layer">
+       <title>Layer 1</title>
+        <rect fill="#ffff00" height="70" width="165" x="179.5" y="146.5"/>
+      </g>
+     </svg>`, {parseSpecialCharSequences: false});
+    cy.get('#tool_source_save').click();
+    cy.get('#tool_undo').click();
+    cy.get('#tool_redo').click(); // test also redo to make the test more comprehensive
+    // if the undo throws an error to the console, the test will fail
+  });
+});