agent: Initialize variable

There is a codepath where it can be used without being filled.
Found by coverity.

1 files changed, 1 insertions, 0 deletions

diff --git a/agent/agent.c b/agent/agent.c
index 8cde228..fb494d3 100644
--- a/agent/agent.c
+++ b/agent/agent.c
@@ -4219,6 +4219,7 @@ agent_recv_message_unlocked (
 
   /* We need an address for packet parsing, below. */
   if (message->from == NULL) {
+    nice_address_init (&from);
     message->from = &from;
   }