Only set backgroundColor if specified in setOptions

lib/graph3d/Graph3d.js

@@ -876,6 +876,7 @@ Graph3d.prototype.setOptions = function (options) {
     if (options.zMax !== undefined) this.defaultZMax = options.zMax;
     if (options.valueMin !== undefined) this.defaultValueMin = options.valueMin;
     if (options.valueMax !== undefined) this.defaultValueMax = options.valueMax;
+    if (options.backgroundColor !== undefined) this._setBackgroundColor(options.backgroundColor);
 
     if (options.cameraPosition !== undefined) cameraPosition = options.cameraPosition;
 
@@ -904,7 +905,7 @@ Graph3d.prototype.setOptions = function (options) {
         }
       }
     }
-    this._setBackgroundColor(options.backgroundColor);
+    
   }
 
   this.setSize(this.width, this.height);