add grouptitle and handle click

Author: archmoj

src/components/legend/handle_click.js

@@ -126,7 +126,7 @@ module.exports = function handleClick(g, gd, numClicks) {
     var thisLegend = fullTrace.legend;
 
     var fullInput = fullTrace._fullInput;
-    var isShape = fullInput._isShape;
+    var isShape = fullInput && fullInput._isShape;
 
     if(!isShape && Registry.traceIs(fullTrace, 'pie-like')) {
         var thisLabel = legendItem.label;

test/image/baselines/text_on_shapes_basic.png

@@ -25,15 +25,15 @@
                 "label":{"text":"top right", "textposition": "top right"}, "xref":"paper","yref":"paper","type":"circle","x0":0.3,"x1":0.35,"y0":0.2,"y1":0.4
             },
             {
-                "showlegend": true, "legendgroup":"g1",
+                "showlegend": true, "legendgroup":"g1", "legendgrouptitle": { "text": "1st group" },
                 "label":{"text":"xanchor right, position not set<br> two lines", "xanchor":"right", "padding": 10, "font": {"family":"Courier New, monospace", "size":20}}, "xref":"paper","yref":"paper","type":"line","x0":0.8,"x1":0.9,"y0":0.8,"y1":0.9
             },
             {
                 "showlegend": true, "legendgroup":"g1",
                 "label":{"text":"position auto, xanchor center, angle -30", "xanchor":"center", "textangle":-30}, "layer":"below","x0":2,"x1":3,"y0":7,"y1":9.5,"opacity":0.5,"fillcolor":"#05e","line":{"width":3,"color":"#025","dash":"dashdot"}
             },
             {
-                "showlegend": true, "legendgroup":"g2",
+                "showlegend": true, "legendgroup":"g2", "legendgrouptitle": { "text": "2nd group" },
                 "label":{"text":"position auto, yanchor top", "yanchor": "top"}, "yref":"paper","type":"line","x0":1.1,"x1":2.4,"y0":0.1,"y1":0.4,"line":{"color":"#039","dash":"dot","width":2}
             },
             {