compression/tests: Fix possible out of bound access CID:1517301

This would fix additional coverity issue:1517285

Signed-off-by: Vinit Agnihotri <vagnihot@redhat.com>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Martin Schwenke <martin@meltin.net>

Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Mon Aug 11 22:59:26 UTC 2025 on atb-devel-224

Author: Vinit Agnihotri

lib/compression/tests/test_lzxpress_plain.c

@@ -363,6 +363,11 @@ static ssize_t attempt_round_trip(TALLOC_CTX *mem_ctx,
 					     comp_written,
 					     decompressed.data,
 					     decompressed.length);
+	if (decomp_written <= 0) {
+		talloc_free(tmp_ctx);
+		return -1;
+	}
+
 	debug_end_timer("decompress", original.length);
 	if (save_name != NULL && LZX_DEBUG_FILES) {
 		char s[300];