fix type casting bug introduced in 03fde5f

Author: rossengeorgiev

cache.manifest

@@ -1,5 +1,5 @@
 CACHE MANIFEST
-# version 53
+# version 54
 
 # gogole maps files
 http://maps.google.com/maps/api/js?v=3.10&sensor=false&key=AIzaSyCOqkcNey4CCyG4X0X5qxHAhCgD8g5DwXg

js/tracker.js

@@ -829,8 +829,8 @@ function graphAddLastPosition(idx) {
 
            if(isInt(v)) $.extend(true, data[i], { noInterpolate: true, lines: { steps: true }});
         }
-        data[i].data.push([ts, v]);
-        if(v < 0) delete plot_options.yaxes[i+1].min;
+        data[i].data.push([ts, parseFloat(v)]);
+        if(parseFloat(v) < 0) delete plot_options.yaxes[i+1].min;
     });
 }