Merge branch 'maction-events' into alpha

Author: dpvc

mathjax3-ts/handlers/html/HTMLMathItem.ts

@@ -75,7 +75,7 @@ export class HTMLMathItem<N, T, D> extends AbstractMathItem<N, T, D> {
             if (this.inputJax.processStrings) {
                 let node = this.start.node as T;
                 if (node === this.end.node) {
-                    if (this.end.n < this.adaptor.value(this.end.node).length) {
+                    if (this.end.n && this.end.n < this.adaptor.value(this.end.node).length) {
                         this.adaptor.split(this.end.node, this.end.n);
                     }
                     if (this.start.n) {

mathjax3-ts/output/chtml/Wrappers/maction.ts

@@ -97,6 +97,14 @@ export class CHTMLmaction<N, T, D> extends CHTMLWrapper<N, T, D> {
             // Add a click handler that changes the selection and rerenders the expression
             //
             node.setEventHandler('click', (event: Event) => {
+                if (!math.start.node) {
+                    //
+                    // If the MathItem was created by hand, it might not have a node
+                    // telling it where to replace the existing math, so set it.
+                    //
+                    math.start.node = math.end.node = math.typesetRoot;
+                    math.start.n = math.end.n = 0;
+                }
                 mml.nextToggleSelection();
                 math.rerender(document);
                 event.stopPropagation();