check array existence before using it

ui/nG6/lib/class.tx_nG6_utils.php

@@ -50,11 +50,13 @@ class tx_nG6_utils {
 		
 		// Create relationships
 		$h_analysis = array();
-		foreach($tree_analyze as $analyze_id => $analyze_infos) {
-			if ($analyze_infos["data"]["parent_id"] == 0) {
-				$h_analysis[$analyze_id] = &$tree_analyze[$analyze_id];
-			} else {
-				$tree_analyze[$analyze_infos["data"]["parent_id"]]["child"][$analyze_id] = &$tree_analyze[$analyze_id]; 
+		if(is_array($tree_analyze)){
+			foreach($tree_analyze as $analyze_id => $analyze_infos) {
+				if ($analyze_infos["data"]["parent_id"] == 0) {
+					$h_analysis[$analyze_id] = &$tree_analyze[$analyze_id];
+				} else {
+					$tree_analyze[$analyze_infos["data"]["parent_id"]]["child"][$analyze_id] = &$tree_analyze[$analyze_id]; 
+				}
 			}
 		}