Fix used-uninitialised warning in fmt_rfc2047.c
Fix used-uninitialised warning in fmt_rfc2047.c

Fix a used-uninitialised warning in fmt_rfc2047.c.
I don't think it can actually be used uninitialised, but the
code is too complicated for the compiler to realise this.

Signed-off-by: Peter Maydell <d394516ed9d75c1df35a03cbacdc6bc631d6ff97@chiark.greenend.org.uk>

mcr/nmh,dscho/nmh,mcr/nmh,dscho/nmh,dscho/nmh,dscho/nmh