Support LineAnnotations with empty /Rect-entries (issue 6564)

This extends PR 13033 slightly, with a heuristic to support corrupt PDF documents where the `LineAnnotation`s have an empty /Rect-entry. Please note that while I have no idea if this is "correct", this patch at least makes us output the same /BBox as re-saving in Adobe Reader does.

src/core/annotation.js

@@ -23,6 +23,7 @@ import {
   assert,
   escapeString,
   getModificationDate,
+  isArrayEqual,
   isAscii,
   isString,
   OPS,
@@ -2291,6 +2292,17 @@ class LineAnnotation extends MarkupAnnotation {
 
       const borderWidth = this.borderStyle.width;
 
+      // If the /Rect-entry is empty, create a fallback rectangle such that we
+      // get similar rendering/highlighting behaviour as in Adobe Reader.
+      if (isArrayEqual(this.rectangle, [0, 0, 0, 0])) {
+        this.rectangle = [
+          this.data.lineCoordinates[0] - 2 * borderWidth,
+          this.data.lineCoordinates[1] - 2 * borderWidth,
+          this.data.lineCoordinates[2] + 2 * borderWidth,
+          this.data.lineCoordinates[3] + 2 * borderWidth,
+        ];
+      }
+
       this._setDefaultAppearance({
         xref: parameters.xref,
         extra: `${borderWidth} w`,