Make 'auto' to function as 'array' when [] present

Author: ayjayt

src/plots/cartesian/axes.js

@@ -1324,7 +1324,8 @@ function arrayTicks(ax, majorOnly) {
         if((majorOnly !== undefined) && ((majorOnly && isMinor) || (majorOnly === false && !isMinor))) continue;
         if(isMinor && !ax.minor) continue;
         var targetAxis = (!isMinor ? ax : ax.minor);
-        var vals = ax.tickmode === 'array' ? targetAxis.tickvals : targetAxis._mappedTickvals;
+        // if auto w/ array in tickval, is implicit 'array'
+        var vals = ax.tickmode === 'array' || ax.tickmode === 'auto' ? targetAxis.tickvals : targetAxis._mappedTickvals;
         var text = !isMinor ? ax.ticktext : [];
         if(!vals) continue;