fix(graph): fix for when data min/max delta is zero and negative and grid y…

fix(graph): fix for when data min/max delta is zero and negative and grid y min/max is auto, fixes #6980

public/vendor/flot/jquery.flot.js

@@ -1663,15 +1663,17 @@ Licensed under the MIT license.
                 // Grafana fix: wide Y min and max using increased wideFactor
                 // when all series values are the same
                 var wideFactor = 0.25;
-                var widen = max == 0 ? 1 : max * wideFactor;
+                var widen = Math.abs(max == 0 ? 1 : max * wideFactor);
 
-                if (opts.min == null)
+                if (opts.min == null) {
                   min -= widen;
+                }
                 // always widen max if we couldn't widen min to ensure we
                 // don't fall into min == max which doesn't work
-                if (opts.max == null || opts.min != null)
+                if (opts.max == null || opts.min != null) {
                   max += widen;
                 }
+            }
             else {
                 // consider autoscaling
                 var margin = opts.autoscaleMargin;