check_buildlog() probes $warnings_file with -f even when WARNINGS_FILE is
not configured. Perl warns about the uninitialized value and adds noise to
the test log, which can hide the output we actually care about.

Check that WARNINGS_FILE is defined before testing whether the file exists.

Fixes: 4283b169abfb ("ktest: Add make_warnings_file and process full warnings")
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
---
 tools/testing/ktest/ktest.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/ktest/ktest.pl b/tools/testing/ktest/ktest.pl
index 001c4df9f7df..f48ee64c69da 100755
--- a/tools/testing/ktest/ktest.pl
+++ b/tools/testing/ktest/ktest.pl
@@ -2508,7 +2508,7 @@ sub check_buildlog {
     my $save_no_reboot = $no_reboot;
     $no_reboot = 1;
 
-    if (-f $warnings_file) {
+    if (defined($warnings_file) && -f $warnings_file) {
 	open(IN, $warnings_file) or
 	    dodie "Error opening $warnings_file";
 

-- 
2.53.0