Improve validation in the Catalog.prototype.openAction getter

When the /OpenAction data is an Array we're currently using it as-is which could theoretically cause problems in corrupt PDF documents, hence we ensure that a "raw" destination is actually valid. (This change is covered by existing unit-tests.)

*Note:* In the Dictionary case we're using the `Catalog.parseDestDictionary` method, which already handles all of the necessary validation.

src/core/catalog.js

@@ -1029,7 +1029,7 @@ class Catalog {
       } else if (resultObj.action) {
         openAction.action = resultObj.action;
       }
-    } else if (Array.isArray(obj)) {
+    } else if (isValidExplicitDest(obj)) {
       openAction.dest = obj;
     }
     return shadow(