Backport !2887 “glocalfileinfo: Ensure we always sniff some data to get the content type” to glib-2-74
In case the XDG database is not initialized yet we may try to sniff a
0-length data, making our content-type routines to mark non-empty files
as application/x-zerosize
.
This is wrong, so in case the sniff size is not set, let's just try to read the default value. To avoid false-application/x-zerosize results (that are not something we want as per legacy assumptions).
See: https://bugzilla.gnome.org/show_bug.cgi?id=755795
Fixes: #2742 (closed)
Trivial backport of !2887 (merged) to glib-2-74
.