Remove empty space on comment indentation

Applying the patch I got some warnings:

```BASH
$ git apply 1381.diff
1381.diff:3907: space before tab in indent.
 		----------------------------------------
1381.diff:3908: space before tab in indent.
 		|   id |  par |  lft |  rgt | lvl
1381.diff:3909: space before tab in indent.
 		----------------------------------------
1381.diff:3910: space before tab in indent.
 		|    1 |    0 |    0 |   15 |   0
1381.diff:3911: space before tab in indent.
 		|  101 |    1 |    1 |    2 |   1
warning: squelched 7 whitespace errors
warning: 12 lines add whitespace errors.
```