iconv() segfaults if the invalid multibyte character 0xffff is input when converting from IBM930

Issue

• When convirting IBM930 code with iconv(), if IBM930 code which includes invalid multibyte character "0xffff" is specified, then iconv() segfaults.
• When iconv command is performed with such input, it also segfaults.

# echo '0x0e 0x43 0x8c 0xff 0xff 0x43 0xbd 0x43 0xbd' | xxd -r | iconv -f IBM930 -t UTF-8
Segmentation fault