Prevent PartialEvaluator_buildFormXObject from failing if the Matrix or BBox contains indirect objects

This patch fixes yet another instance of bad PDF data, specifically a case where the `BBox` array contains indirect objects (i.e. `Ref`s).

Fixes the missing image in http://www.int.washington.edu/talks/WorkShops/int_08_37W/People/Franz_M/Franz.pdf#page=24. *Note:* There are missing images on a number of the pages in that file.

src/core/evaluator.js

@@ -126,8 +126,8 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
                                                                  xobj, smask,
                                                                  operatorList,
                                                                  initialState) {
-      var matrix = xobj.dict.get('Matrix');
-      var bbox = xobj.dict.get('BBox');
+      var matrix = xobj.dict.getArray('Matrix');
+      var bbox = xobj.dict.getArray('BBox');
       var group = xobj.dict.get('Group');
       if (group) {
         var groupOptions = {

test/pdfs/.gitignore

@@ -3,6 +3,7 @@
 
 !tracemonkey.pdf
 !franz.pdf
+!franz_2.pdf
 !issue2391-1.pdf
 !issue2391-2.pdf
 !issue5801.pdf

test/test_manifest.json

@@ -527,6 +527,14 @@
        "type": "eq",
        "about": "Type1 font with |Ref|s in the Differences array of the Encoding dictionary."
     },
+    {  "id": "franz_2",
+       "file": "pdfs/franz_2.pdf",
+       "md5": "9d301ed8816e879891115b5cc3c39559",
+       "link": false,
+       "rounds": 1,
+       "type": "eq",
+       "about": "XObject with BBox array containing indirect object."
+    },
     {  "id": "issue4934",
        "file": "pdfs/issue4934.pdf",
        "md5": "6099da44f677702ae65a648b51a2226d",