reset _numBoxes/_numViolins before calc

Author: antoinerg

src/plots/plots.js

@@ -2887,6 +2887,9 @@ plots.doCalcdata = function(gd, traces) {
     // Sort axis categories per value if specified
     var sorted = sortAxisCategoriesByValue(axList, gd);
     if(sorted.length) {
+        // how many box/violins plots do we have (in case they're grouped)
+        fullLayout._numBoxes = 0;
+        fullLayout._numViolins = 0;
         // If a sort operation was performed, run calc() again
         for(i = 0; i < sorted.length; i++) calci(sorted[i], true);
         for(i = 0; i < sorted.length; i++) calci(sorted[i], false);