As clipboard_find_supported_format_by_mime_type() can return -1 if it
can't find out an index avoid trying to print outside of the array.
Fixes the following warnings triggered when enabling FORTIFY_SOURCE
combined with optimizations (-O)
../libweston/backend-rdp/rdpclip.c:1114:17: error: array subscript -1 is below array bounds of ‘uint32_t[5]’ {aka ‘unsigned int[5]’} [-Werror=array-bounds]
1114 | weston_log("RDP %s (%p:%s) specified format \"%s\" index:%d formatId:%d is not supported by client\n",
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1115 | __func__, source, clipboard_data_source_state_to_string(source),
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1116 | mime_type, index, source->client_format_id_table[index]);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../libweston/backend-rdp/rdpclip.c:131:18: note: while referencing ‘client_format_id_table’
131 | uint32_t client_format_id_table[RDP_NUM_CLIPBOARD_FORMATS];
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
(cherry picked from commit 9455ad7c7c07fdb8218330f449c97be73f695742)