ZTS: Fix summary page creation again - second try

In PR #16599 I used 'return' like in C - which is wrong :/
This fix generates the summary as needed.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tino Reichardt <milky-zfs@mcmilk.de>
Closes #16611

.github/workflows/scripts/qemu-9-summary-page.sh

@@ -11,12 +11,10 @@ function output() {
 }
 
 function outfile() {
-  test -s "$1" || return
   cat "$1" >> "out-$logfile.md"
 }
 
 function outfile_plain() {
-  test -s "$1" || return
   output "<pre>"
   cat "$1" >> "out-$logfile.md"
   output "</pre>"
@@ -45,6 +43,8 @@ if [ ! -f out-1.md ]; then
     tar xf "$tarfile"
     test -s env.txt || continue
     source env.txt
+    # when uname.txt is there, the other files are also ok
+    test -s uname.txt || continue
     output "\n## Functional Tests: $OSNAME\n"
     outfile_plain uname.txt
     outfile_plain summary.txt