mkvparser: reject files w/multiple ProjectionPrivate

further validation of the Projection element could be added, this check
avoids a memory leak

Bug: b/148840606
Change-Id: I5dd7129970bc4df9d21f414865d1b7983493815e
diff --git a/mkvparser/mkvparser.cc b/mkvparser/mkvparser.cc
index ace65bd..fe0f25e 100644
--- a/mkvparser/mkvparser.cc
+++ b/mkvparser/mkvparser.cc
@@ -5229,6 +5229,8 @@
 
       projection_ptr->type = static_cast<ProjectionType>(projection_type);
     } else if (child_id == libwebm::kMkvProjectionPrivate) {
+      if (projection_ptr->private_data != NULL)
+        return false;
       unsigned char* data = SafeArrayAlloc<unsigned char>(1, child_size);
 
       if (data == NULL)