Fixed compilation issue on Mint 14

Hi,

First of all thank you very much for the hexBlocker tool. I think this really has potential, more than any of the other tools I have seen so far for this purpose.

To the case: I have taken the freedom to fix the compilation issue I described in http://www.cfd-online.com/Forums/openfoam-meshing/114773-hexblocker-gui-blockmeshdict-alpha-release.html#post414659 I don't know why it failed on my machine, but this fix seemed to do the trick. I believe it will work on other machines too. It is not as elegant as your original code tough, it's sad that it did not work.

Best regards,
Håkon  Strandenes