Hide chart when setData is passed empty or null array. (Fixes #142)

lib/morris.bar.coffee

@@ -116,6 +116,7 @@ class Morris.Bar extends Morris.Grid
   # hit test - returns the index of the row beneath the given coordinate
   #
   hitTest: (x, y) ->
+    return null if @data.length == 0
     x = Math.max(Math.min(x, @right), @left)
     Math.min(@data.length - 1,
       Math.floor((x - @left) / (@width / @data.length)))

lib/morris.grid.coffee

@@ -94,6 +94,12 @@ class Morris.Grid extends Morris.EventEmitter
   # Update the data series and redraw the chart.
   #
   setData: (data, redraw = true) ->
+    if !data? or data.length == 0
+      @data = []
+      @raphael.clear()
+      @hover.hide() if @hover?
+      return
+
     ymax = if @cumulative then 0 else null
     ymin = if @cumulative then 0 else null
 

lib/morris.line.coffee

@@ -59,6 +59,7 @@ class Morris.Line extends Morris.Grid
   # hit test - returns the index of the row beneath the given coordinate
   #
   hitTest: (x, y) ->
+    return null if @data.length == 0
     # TODO better search algo
     for r, index in @data.slice(1)
       break if x < (r._x + @data[index]._x) / 2

spec/lib/grid/set_data_spec.coffee

@@ -174,4 +174,15 @@ describe 'Morris.Grid#setData', ->
     line.ymax.should == 16
     line.data.map((row) -> row.y).should.deep.equal [[13.5], [12], [16], [14]]
 
-
+  it 'should clear the chart when empty data is supplied', ->
+    line = Morris.Line
+      element: 'graph',
+      data: [{x: 2, y: '12'}, {x: 1, y: '13.5'}, {x: 4, y: '14'}, {x: 3, y: '16'}]
+      xkey: 'x'
+      ykeys: ['y']
+      labels: ['y']
+    line.data.length.should.equal 4
+    line.setData([])
+    line.data.length.should.equal 0
+    line.setData([{x: 2, y: '12'}, {x: 1, y: '13.5'}, {x: 4, y: '14'}, {x: 3, y: '16'}])
+    line.data.length.should.equal 4