runtests.pl: fix warning 'use of uninitialized value'

follow-up to a9a7b60

Closes #2428

diff --git a/tests/runtests.pl b/tests/runtests.pl
index 6503bf779704c35665b15ed3f9c93a3f6c190d3a..f9172007b3f0a2a1c9a4845e26367e1b49ab2580 100755 (executable)
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -3909,7 +3909,8 @@ sub singletest {
 
     if((!$cmdhash{'option'}) || ($cmdhash{'option'} !~ /no-output/)) {
         #We may slap on --output!
-        if (!@validstdout || $cmdhash{'option'} =~ /force-output/) {
+        if (!@validstdout ||
+                ($cmdhash{'option'} && $cmdhash{'option'} =~ /force-output/)) {
             $out=" --output $CURLOUT ";
         }
     }