Fixed a bug that happens panic when use global gitignore.
Fixed a bug that happens panic when use global gitignore.

yuya-takeyama/the_platinum_searcher,syohex/the_platinum_searcher,monochromegane/the_platinum_searcher,cmars/tools,cmars/tools,cmars/tools,aeruder/the_platinum_searcher,cmars/tools,DaSea/the_platinum_searcher,tw4452852/the_platinum_searcher,thomasf/the_platinum_searcher