Add MIME type pattern when using filtered view adds pattern to wrong MIME type

Steps to reproduce:

• open Creator, go to Tools -> Options -> Environment -> MIME Types
• enter a filter, add an additional pattern (and/or Magic thingy)
• hit 'Apply' or switch the current selected item
• remove the filter and check the modified item

Current result:

• the modified item is the index of the unfiltered list

Expected result:

• no matter whether filtering is done or not the correct item is used to modify