From:  "John W. Eaton" <jwe@octave.org>
Subject: Don't crash on filtering an empty vector
Origin: upstream, http://hg.savannah.gnu.org/hgweb/octave/rev/a277ba5da4dc
Bug-Debian: http://bugs.debian.org/567975

--- a/src/DLD-FUNCTIONS/filter.cc
+++ b/src/DLD-FUNCTIONS/filter.cc
@@ -117,6 +117,9 @@
 	}
     }
 
+  if (x_len == 0)
+    return x;
+
   if (norm != static_cast<T>(1.0))
     {
       a = a / norm;