Do not draw a border if neither a Border nor a BS entry is present

Fixes #6179.

src/core/annotation.js

@@ -144,6 +144,13 @@ var Annotation = (function AnnotationClosure() {
             this.borderStyle.setDashArray(array[3]);
           }
         }
+      } else {
+        // There are no border entries in the dictionary. According to the
+        // specification, we should draw a solid border of width 1 in that
+        // case, but Adobe Reader did not implement that part of the
+        // specification and instead draws no border at all, so we do the same.
+        // See also https://github.com/mozilla/pdf.js/issues/6179.
+        this.borderStyle.setWidth(0);
       }
     },