fix delete last line

lib/ace/editor.js

@@ -832,7 +832,7 @@ var Editor =function(renderer, session) {
             var range = new Range(rows.first, 0, rows.last+1, 0)
         else
             var range = new Range(
-                rows.first-1, this.session.getLine(rows.first).length,
+                rows.first-1, this.session.getLine(rows.first-1).length,
                 rows.last, this.session.getLine(rows.last).length
             );
         this.session.remove(range);