xdgmimecache: Fix a signed/unsigned integer comparison warning

This fixes the warning:
```
xdgmimecache.c: In function ‘cache_lookup_icon’:
xdgmimecache.c:84:33: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
   84 |   (((offset) & 0x3) || (offset) > (max) || (n) > ((max) - (offset)) / (record_size))
      |                                 ^
xdgmimecache.c:1106:11: note: in expansion of macro ‘OUT_OF_BOUNDS’
 1137 |       if (OUT_OF_BOUNDS (header, 1, 4, cache->size))
      |           ^~~~~~~~~~~~~
cc1: all warnings being treated as errors
```

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/xdgmimecache.c b/src/xdgmimecache.c
index 6d89f10..8722f8c 100644
--- a/src/xdgmimecache.c
+++ b/src/xdgmimecache.c
@@ -1088,7 +1088,7 @@ _xdg_mime_cache_list_mime_parents (const char *mime)
 }
 
 static const char *
-cache_lookup_icon (const char *mime, int header)
+cache_lookup_icon (const char *mime, size_t header)
 {
   const char *ptr;
   int i, min, max, mid, cmp;