STR#3012 Fix: cairo_make_current(void*, int, int) would not release previously allocated cc in certain conditions.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10026 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
STR#3012 Fix: cairo_make_current(void*, int, int) would not release previously allocated cc in certain conditions, fixed the extra cc non null test condition erronously formulated in previous submission.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10027 ea41ed52-d2ee-0310-a9c1-e6b18d33e121