pdfviewer: more prerequired work to have examples working for transparency work items.

Review URL: https://codereview.chromium.org/21252003

git-svn-id: http://skia.googlecode.com/svn/trunk@10438 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/PdfViewer/generate_code.py b/experimental/PdfViewer/generate_code.py
index 23a8360..0fb566d 100644
--- a/experimental/PdfViewer/generate_code.py
+++ b/experimental/PdfViewer/generate_code.py
@@ -482,7 +482,7 @@
       fileMapperNative.write('  SkPdfObjectType map' + name + '(const SkPdfObject* in) const;\n')
 
       fileMapperNativeCpp.write('SkPdfObjectType SkPdfMapper::map' + name + '(const SkPdfObject* in) const {\n')
-      fileMapperNativeCpp.write('  if (!is' + name + '(in)) return kNone_SkPdfObjectType;\n')
+      fileMapperNativeCpp.write('  if (in == NULL || !is' + name + '(in)) return kNone_SkPdfObjectType;\n')
       fileMapperNativeCpp.write('\n')
       if len(cls.fEnumSubclasses) > 0:
         fileMapperNativeCpp.write('  SkPdfObjectType ret;\n')