xz: Fix a bug with --files and --files0 in raw mode without a suffix.

The following command caused a segmentation fault:

    xz -Fraw --lzma1 --files=foo

when foo was a valid file. The usage of --files or --files0 was not
being checked when compressing or decompressing in raw mode without a
suffix. The suffix checking code was meant to validate that all files
to be processed are "-" (if not writing to standard out), meaning the
data is only coming from standard in. In this case, there were no file
names to check since --files and --files0 store their file name in a
different place.

Later code assumed the suffix was set and caused a segmentation fault.
Now, the above command results in an error.

0 files changed, 0 insertions, 0 deletions