Fix a bug in MatchDecorator where deletions might break updates

FIX: Fix an issue in `MatchDecorator` causing `updateDeco` to sometimes not
do the right thing for deletions.

See https://discuss.codemirror.net/t/bug-with-highlighttrailingwhitespace-and-entering-a-new-line-and-pressing-command-z/9213

Author: marijnh

src/highlight-space.ts

@@ -33,8 +33,7 @@ export function highlightWhitespace() {
 
 const trailingHighlighter = matcher(new MatchDecorator({
   regexp: /\s+$/g,
-  decoration: Decoration.mark({class: "cm-trailingSpace"}),
-  boundary: /\S/,
+  decoration: Decoration.mark({class: "cm-trailingSpace"})
 }))
 
 /// Returns an extension that adds a `cm-trailingSpace` class to all

src/matchdecorator.ts

@@ -118,7 +118,7 @@ export class MatchDecorator {
   private updateRange(view: EditorView, deco: DecorationSet, updateFrom: number, updateTo: number) {
     for (let r of view.visibleRanges) {
       let from = Math.max(r.from, updateFrom), to = Math.min(r.to, updateTo)
-      if (to > from) {
+      if (to >= from) {
         let fromLine = view.state.doc.lineAt(from), toLine = fromLine.to < to ? view.state.doc.lineAt(to) : fromLine
         let start = Math.max(r.from, fromLine.from), end = Math.min(r.to, toLine.to)
         if (this.boundary) {