Bug(?) when filtered by 2 fields of tags type

Hi,
because I try to filtered catalog by 2 tags fields and result was not as expected, I spend some time to code analize.
I think I found bug.
In ModuleCatalog.php about lines 520-530 is code:

Code:

foreach(explode(',', $current[$field]) as $tag) $tags[] = (int)$tag;

Bug(?) is, when i have 2 fields of tag type, this line added both of tag.

eg. firse filtr a = 1, second filtr a = 2. For first field tag is ok and $tags array have 1 value "1", but for second, tags array has TWO values 1 and 2.
This is because array tag IS NOT cleaerd between loop step...
I added for test one line

Code:

$tags=array(); //line added foreach(explode(',', $current[$field]) as $tag) $tags[] = (int)$tag;

and now my result looks ok.

Can you check, this is bug or intended ?