Fix possible crash on iconv_close with bad descriptor.
Fix possible crash on iconv_close with bad descriptor.

This is an attempt to fix Shotcut bug 146, which appears to be a result
of closing an invalid conversion descriptor, which might be due to a
failure to get the Windows code page for some locales.

mltframework/mlt,j-b-m/mlt,siddharudh/mlt,mltframework/mlt,mltframework/mlt,xzhavilla/mlt,mltframework/mlt,xzhavilla/mlt,siddharudh/mlt,mltframework/mlt,siddharudh/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,siddharudh/mlt,xzhavilla/mlt,j-b-m/mlt,xzhavilla/mlt,siddharudh/mlt,j-b-m/mlt,siddharudh/mlt,mltframework/mlt,xzhavilla/mlt,xzhavilla/mlt,siddharudh/mlt,xzhavilla/mlt,siddharudh/mlt,j-b-m/mlt,xzhavilla/mlt,xzhavilla/mlt,siddharudh/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt