Bounding the xLabelAngle option.

lib/morris.grid.coffee

@@ -21,6 +21,9 @@ class Morris.Grid extends Morris.EventEmitter
     if typeof @options.units is 'string'
       @options.postUnits = options.units
 
+    # bound xLabelAngle to 0..90
+    @options.xLabelAngle = Math.max(0, Math.min(90, @options.xLabelAngle))
+
     # the raphael drawing instance
     @raphael = new Raphael(@el[0])
 

morris.js

@@ -84,6 +84,7 @@
       if (typeof this.options.units === 'string') {
         this.options.postUnits = options.units;
       }
+      this.options.xLabelAngle = Math.max(0, Math.min(90, this.options.xLabelAngle));
       this.raphael = new Raphael(this.el[0]);
       this.elementWidth = null;
       this.elementHeight = null;