fix 'failed to install translation' message when misc/locale in hedgewars.ini is empty (which is *always* when 'system default' is selected)

     1

[patterns]

     2

**.h = native

     3

**.c = native

     4

**.cpp = native

     5

**.lua = native

     6

**.txt = native

     7

**.pas = native

     8

**.inc = native

     9

**.hs = native