Move init of ctx up before we setup the monitors. I think in some cases we can calls functions that assume ctx has a value. Uncaught%20TypeError%3A%20Cannot%20read%20properties%20of%20undefined%20(reading%20'getImageData')

web/skins/classic/views/js/montagereview.js

@@ -985,6 +985,19 @@ function initPage() {
     });
   });
 
+  if ( !liveMode ) {
+    canvas = document.getElementById('timeline');
+
+    canvas.addEventListener('mousemove', mmove, false);
+    canvas.addEventListener('touchmove', tmove, false);
+    canvas.addEventListener('mousedown', mdown, false);
+    canvas.addEventListener('mouseup', mup, false);
+    canvas.addEventListener('mouseout', mout, false);
+
+    ctx = canvas.getContext('2d');
+    drawGraph();
+  }
+
   for ( var i = 0, len = monitorPtr.length; i < len; i += 1 ) {
     var monId = monitorPtr[i];
     if ( !monId ) continue;
@@ -1006,18 +1019,6 @@ function initPage() {
     }
   } // end foreach monitor
 
-  if ( !liveMode ) {
-    canvas = document.getElementById('timeline');
-
-    canvas.addEventListener('mousemove', mmove, false);
-    canvas.addEventListener('touchmove', tmove, false);
-    canvas.addEventListener('mousedown', mdown, false);
-    canvas.addEventListener('mouseup', mup, false);
-    canvas.addEventListener('mouseout', mout, false);
-
-    ctx = canvas.getContext('2d');
-    drawGraph();
-  }
   setSpeed(speedIndex);
   //setFit(fitMode);  // will redraw
   //setLive(liveMode);  // will redraw

web/skins/classic/views/js/montagereview.js.php

@@ -239,6 +239,6 @@ echo "];\n";
 var cWidth;   // save canvas width
 var cHeight;  // save canvas height
 var canvas;   // global canvas definition so we don't have to keep looking it up
-var ctx;
+var ctx = null;
 var underSlider;    // use this to hold what is hidden by the slider
 var underSliderX;   // Where the above was taken from (left side, Y is zero)