Initialize committers variable

Prevented the check for variable collision detection from
previous commit: first time the committers property was
null.

scripts/gitolite/rebuild_gitolite.php

@@ -66,6 +66,7 @@ class Configuration {
     $this->config_file = "$gitolite_root/conf/gitolite.conf";
 
     $this->collectSystemPublicKeys();
+    $this->committers = array();
 
     if (!file_exists($this->config_file)) {
       die("Not found: $this->config_file\n");