model.js: Don't select virtual clones

The previous code was fantastically overcomplicated
(which could be summarised by “WTF”).

Now we make use of the isVirtual() function to determine
is a clone can be selected.

Commit performed by trio-programming: @tydax @RyanHerb @mikael-s

browser/js/model.js

@@ -773,11 +773,9 @@ changeCloneNotation: function(cloneNotationType) {
         console.log("select() (clone " + cloneID + ")");
 
         // others shouldn't be selectable
-        var posOthers = {}; 
-        for (var i = this.clones.length - this.system_available.length; i <= this.clones.length - 1; i++) {
-            posOthers[i]='';
-            }
-        if (cloneID in posOthers) {return 0;};
+        if (m.clones[cloneID].isVirtual()) {
+            return 0;
+        }
 
         if (this.clone(cloneID).isSelected()) {
             this.clone(cloneID).select = false;