simplify subplot creation if-statement

Author: etpinard

src/plots/geo/index.js

@@ -49,7 +49,7 @@ exports.plot = function plotGeo(gd) {
             geo = fullLayout[geoId]._subplot;
 
         // If geo is not instantiated, create one!
-        if(geo === undefined) {
+        if(!geo) {
             geo = new Geo({
                 id: geoId,
                 graphDiv: gd,

src/plots/ternary/index.js

@@ -41,7 +41,7 @@ exports.plot = function plotTernary(gd) {
             ternary = fullLayout[ternaryId]._subplot;
 
         // If ternary is not instantiated, create one!
-        if(ternary === undefined) {
+        if(!ternary) {
             ternary = new Ternary({
                 id: ternaryId,
                 graphDiv: gd,