Don't try to drag an empty selection

Author: marijnh

lib/codemirror.js

@@ -275,7 +275,8 @@ var CodeMirror = (function() {
       } else { lastClick = now; }
 
       var last = start, going;
-      if (dragAndDrop && !posLess(start, sel.from) && !posLess(sel.to, start)) {
+      if (dragAndDrop && !posEq(sel.from, sel.to) &&
+          !posLess(start, sel.from) && !posLess(sel.to, start)) {
         // Let the drag handler handle this.
         return;
       }