rm subplotId key from clickannotations event data when falsy

Author: etpinard

src/components/annotations/draw.js

@@ -133,13 +133,19 @@ function drawRaw(gd, options, index, subplotId, xa, ya) {
         .call(setCursor, 'default')
         .on('click', function() {
             gd._dragging = false;
-            gd.emit('plotly_clickannotation', {
+
+            var eventData = {
                 index: index,
-                subplotId: subplotId,
                 annotation: options._input,
                 fullAnnotation: options,
                 event: d3.event
-            });
+            };
+
+            if(subplotId) {
+                eventData.subplotId = subplotId;
+            }
+
+            gd.emit('plotly_clickannotation', eventData);
         });
 
     if(options.hovertext) {