Bug #232453 --> ldap quick search and advanced search does not honor search filters

when applied to the ldap directory properties dialog.

r=dmose
sr=bienvenu

mailnews/addrbook/src/nsLDAPAutoCompleteSession.cpp

@@ -909,7 +909,7 @@ nsLDAPAutoCompleteSession::StartLDAPSearch()
     // no need to AND in an empty search term, so leave prefix and suffix empty
     //
     nsCAutoString prefix, suffix;
-    if (!urlFilter.Equals(NS_LITERAL_CSTRING("(objectclass=*)"))) {
+    if (urlFilter.Length() && !urlFilter.Equals(NS_LITERAL_CSTRING("(objectclass=*)"))) {
 
         // if urlFilter isn't parenthesized, we need to add in parens so that
         // the filter works as a term to &