Apply rovv's patch for bug 864: avoid null error on detached signature handling failure.

svn:r17446

ChangeLog

@@ -24,6 +24,13 @@ Changes in version 0.2.1.8-alpha - 2008-??-??
       could make gcc generate non-functional binary search code. Bugfix
       on 0.2.0.10-alpha.
     - Build correctly on platforms without socklen_t.
+    - Avoid potential crash on internal error during signature collection.
+      Fixes bug 864.  Patch from rovv.
+
+  o Minor features:
+    - Report the case where all signatures in a detached set are rejected
+      differently than the case where there is an error handling the detached
+      set.
 
   o Minor features (controller):
     - Return circuit purposes in response to GETINFO circuit-status.  Fixes

src/or/dirvote.c

@@ -2082,13 +2082,15 @@ dirvote_add_signatures_to_pending_consensus(
     tor_free(pending_consensus_signatures);
     pending_consensus_signatures = new_detached;
     *msg_out = "Signatures added";
+  } else if (r == 0) {
+    *msg_out = "Signatures ignored";
   } else {
     goto err;
   }
 
   goto done;
  err:
-  if (!msg_out)
+  if (!*msg_out)
     *msg_out = "Unrecognized error while adding detached signatures.";
  done:
   if (sigs)