diff -r eed4cdee4ed0 -r 973a136cfbd0 web/res/js/live-polemic.js
--- a/web/res/js/live-polemic.js	Mon Apr 15 13:24:53 2013 +0200
+++ b/web/res/js/live-polemic.js	Mon Apr 15 13:40:50 2013 +0200
@@ -353,6 +353,9 @@
 }
 
 function flattenDateStruct(slices, target_level) {
+	if (!slices || !slices.length) {
+		return [];
+	}
     var current_level = slices[0].level,
         result = [];
     if (current_level < target_level) {
@@ -375,6 +378,9 @@
 }
 
 function trimFDS() {
+	if (!slices || !slices.length) {
+		return [];
+	}
     var slices = flattenDateStruct(twCx.timeline, twCx.timeLevel);
     while (slices[0].tweets.length == 0) {
         slices.splice(0,1);
@@ -524,7 +530,7 @@
 }
 
 function tlIdFromPos(x, y, outside) {
-    if (!twCx.tlOnDisplay) {
+    if (!twCx.tlOnDisplay || !twCx.tlOnDisplay.length) {
         return;
     }
     var ligne = Math.min( twCx.tlOnDisplay.length - 1, Math.max( 0, Math.floor(( twCx.tlHeight - y ) / twCx.scaleY) ) ),
@@ -835,6 +841,9 @@
     }
     
     twCx.tlOnDisplay = trimFDS();
+    if (!twCx.tlOnDisplay || !twCx.tlOnDisplay.length) {
+    	return;
+    }
     twCx.scaleY = twCx.tlHeight / twCx.tlOnDisplay.length;
     var maxTweets = 0,
         startTl = 0,