Ahh... yes, that is right. 4.9 branch still says 4.9.1 and not 4.9.2. So actually it is those who compiled kde-baseapps before its 4.9 branch was fixed to disallow the compilation of the dirfilter plugin unless it finds kdelibs 4.9.2 are the ones who will encounter this problem. Anyhow, either removing the plugin from your system as previously stated or like me changing the version number to 4.9.2 in kdelibs' CMakeLists.txt file are your only two options. At least until the version number in kdelibs 4.9 branch is bumped to 4.9.2.