pie & sunburst: pass empty text string to texttemplate

Author: antoinerg

src/traces/pie/plot.js

@@ -991,8 +991,8 @@ function formatSliceLabel(gd, pt, cd0) {
             pt.text = '';
         } else {
             var obj = makeTemplateVariables(pt);
-            var ptTx = helpers.getFirstFilled(trace.text, pt.pts);
-            if(isValidTextValue(ptTx)) obj.text = ptTx;
+            var ptTx = Lib.castOption(trace, pt.i, 'text');
+            if(isValidTextValue(ptTx) || ptTx === '') obj.text = ptTx;
             pt.text = Lib.texttemplateString(txt, obj, gd._fullLayout._d3locale, obj, trace._meta || {});
         }
     }

src/traces/sunburst/plot.js

@@ -718,7 +718,7 @@ function formatSliceLabel(pt, trace, fullLayout) {
         obj.color = cdi.color;
     }
     var ptTx = Lib.castOption(trace, cdi.i, 'text');
-    if(Lib.isValidTextValue(ptTx)) obj.text = ptTx;
+    if(Lib.isValidTextValue(ptTx) || ptTx === '') obj.text = ptTx;
     obj.customdata = Lib.castOption(trace, cdi.i, 'customdata');
     return Lib.texttemplateString(txt, obj, fullLayout._d3locale, obj, trace._meta || {});
 }