Convert multiple rows to one row with this code in SQL?

my table is:

id   val     catid
 1   title1     7
 2   text1      8
 3   title2     7
 4   text2      8

I want combine rows as this:

val1     val2
title1     text1
title2     text2

I used this query:

select
 (case when catid = 7 then val end) val1,
 (case when catid = 8 then val end) val2
from mytable

But my result is:

val1     val2
title1     Null
Null       text1
title1     Null
Null       text2

How to fix it? Thanks