Fix a compile error on zero mrbgem case.
MODIFY
tasks/mrbgems.rake
tasks/mrbgems.rake
@@ -34,11 +34,13 @@ MRuby.each_target do
f.puts %Q[#include <mruby.h>]
f.puts %Q[]
f.write gem_func_decls
+ unless gem_final_calls.empty?
f.puts %Q[]
f.puts %Q[static void]
f.puts %Q[mrb_final_mrbgems(mrb_state *mrb) {]
f.write gem_final_calls
f.puts %Q[}]
+ end
f.puts %Q[]
f.puts %Q[void]
f.puts %Q[mrb_init_mrbgems(mrb_state *mrb) {]

Fix a compile error on zero mrbgem case.