3 files changed, 5 insertions, 5 deletions

diff --git a/index.php b/index.php
index 41e710f..c7f1642 100644
--- a/index.php
+++ b/index.php
@@ -9,7 +9,7 @@ html_start();
 $h = array();
 
 # show all categorized hosts
-if (is_array($CONFIG['cat'])) {
+if (isset($CONFIG['cat']) && is_array($CONFIG['cat'])) {
         foreach($CONFIG['cat'] as $cat => $hosts) {
                 host_summary($cat, $hosts);
                 $h = array_merge($h, $hosts);
diff --git a/rrd.php b/rrd.php
index a873bf7..1b5997b 100644
--- a/rrd.php
+++ b/rrd.php
@@ -8,9 +8,9 @@ if ($file = validateRRDPath($CONFIG['datadir'], $_SERVER['PATH_INFO'])) {
         header('Content-Type: application/octet-stream');
         header('Content-Disposition: attachment; filename='.basename($file));
         header("Expires: " .date(DATE_RFC822,strtotime($CONFIG['cache']." seconds")));
-    ob_clean();
-    flush();
-    readfile($file);
+        if(ob_get_length()) ob_clean();
+        flush();
+        readfile($file);
 } else {
         header('HTTP/1.0 403 Forbidden');
 
diff --git a/type/GenericStacked.class.php b/type/GenericStacked.class.php
index 63d7f33..3f249c7 100644
--- a/type/GenericStacked.class.php
+++ b/type/GenericStacked.class.php
@@ -37,7 +37,7 @@ class Type_GenericStacked extends Type_Default {
                         if ($i == (count($sources)-1))
                                 $rrdgraph[] = sprintf('CDEF:area_%s=avg_%1$s', crc32hex($sources[$i]));
                         else
-                                $rrdgraph[] = sprintf('CDEF:area_%s=area_%s,avg_%1$s,+', crc32hex($sources[$i]), crc32hex($sources[$i+1]));
+                                $rrdgraph[] = sprintf('CDEF:area_%s=area_%s,avg_%1$s,ADDNAN', crc32hex($sources[$i]), crc32hex($sources[$i+1]));
                 }
 
                 $c = 0;