Don't allow raneming domains to empty strings

It may cause unwanted behaviour (of course, is there any wanted one for
that case?) so we should rather disable the possibility of doing so.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1320893

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

src/libvirt-domain.c

@@ -8790,7 +8790,7 @@ virDomainRename(virDomainPtr dom,
 
     virResetLastError();
     virCheckDomainReturn(dom, -1);
-    virCheckNonNullArgGoto(new_name, error);
+    virCheckNonEmptyStringArgGoto(new_name, error);
     virCheckReadOnlyGoto(dom->conn->flags, error);
 
     if (dom->conn->driver->domainRename) {