Fix error when there's no writeable addressbook source (#1489162)

CHANGELOG

@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix error when there's no writeable addressbook source (#1489162)
 - Add option show_real_foldernames to disable localization of special folders
 - Fix zipdownload plugin issue with filenames charset (#1489156)
 - Fix database cache expunge issues (#1489149)

program/include/rcmail.php

@@ -228,6 +228,11 @@ class rcmail extends rcube
     }
 
     if (!$contacts) {
+      // there's no default, just return
+      if ($default) {
+        return null;
+      }
+
       self::raise_error(array(
         'code' => 700, 'type' => 'php',
         'file' => __FILE__, 'line' => __LINE__,

program/steps/mail/show.inc

@@ -275,9 +275,13 @@ function rcmail_contact_exists($email)
   if ($email) {
     // @TODO: search in all address books?
     $CONTACTS = $RCMAIL->get_address_book(-1, true);
-    $existing = $CONTACTS->search('email', $email, true, false);
-    if ($existing->count)
-      return true;
+
+    if (is_object($CONTACTS)) {
+      $existing = $CONTACTS->search('email', $email, true, false);
+      if ($existing->count) {
+        return true;
+      }
+    }
   }
 
   return false;