filter: un-break the SWF export dialog

The mpResMgr is no longer initialized but still checked.
(regression from 191dc43f97ed8bec78ee540676a91815cad71104)

Change-Id: I8330a74e9209eaca1fee70e7b8ba332482fa0c1d
(cherry picked from commit 6e4a4af525923eb6c2b24f6ac0c9936efe827ca3)