Fixes #225, grid min not sent to graphite png renderer when set to 0

src/app/directives/grafanaGraph.js

@@ -318,7 +318,7 @@ function (angular, $, kbn, moment, _) {
           }
         });
 
-        function render_panel_as_graphite_png(url) {
+        function render_panel_as_graphite_png(url) {          
           url += '&width=' + elem.width();
           url += '&height=' + elem.css('height').replace('px', '');
           url += '&bgcolor=1f1f1f'; // @grayDarker & @kibanaPanelBackground
@@ -327,8 +327,8 @@ function (angular, $, kbn, moment, _) {
           url += scope.panel.fill !== 0 ? ('&areaAlpha=' + (scope.panel.fill/10).toFixed(1)) : '';
           url += scope.panel.linewidth !== 0 ? '&lineWidth=' + scope.panel.linewidth : '';
           url += scope.panel.legend ? '' : '&hideLegend=true';
-          url += scope.panel.grid.min ? '&yMin=' + scope.panel.grid.min : '';
-          url += scope.panel.grid.max ? '&yMax=' + scope.panel.grid.max : '';
+          url += scope.panel.grid.min !== null ? '&yMin=' + scope.panel.grid.min : '';
+          url += scope.panel.grid.max !== null ? '&yMax=' + scope.panel.grid.max : '';
           url += scope.panel['x-axis'] ? '' : '&hideAxes=true';
           url += scope.panel['y-axis'] ? '' : '&hideYAxis=true';