diff -r 2986137093c6 -r a6e2a667b0a8 src/Pure/PIDE/command.scala
--- a/src/Pure/PIDE/command.scala	Wed Aug 12 03:07:01 2015 +0200
+++ b/src/Pure/PIDE/command.scala	Wed Aug 12 13:53:51 2015 +0200
@@ -413,6 +413,9 @@
   def blobs_names: List[Document.Node.Name] =
     for (Exn.Res((name, _)) <- blobs) yield name
 
+  def blobs_undefined: List[Document.Node.Name] =
+    for (Exn.Res((name, None)) <- blobs) yield name
+
   def blobs_defined: List[(Document.Node.Name, SHA1.Digest)] =
     for (Exn.Res((name, Some((digest, _)))) <- blobs) yield (name, digest)