singleuse.pl: fix string warning

"Use of uninitialized value $unittests in concatenation on line 170"

Closes #19266

diff --git a/scripts/singleuse.pl b/scripts/singleuse.pl
index b4cbe3ff4a12fc5e2972d5379e68e00aad15b909..3ce5dda4423b3fc7b736f6df5e248bc13b621524 100755 (executable)
--- a/scripts/singleuse.pl
+++ b/scripts/singleuse.pl
@@ -36,7 +36,7 @@
 use strict;
 use warnings;
 
-my $unittests;
+my $unittests="";
 if(@ARGV && $ARGV[0] eq "--unit") {
     $unittests = "tests/unit ";
     shift @ARGV;