MDEV-33750: Rework MyISAM recovery script

Make small adjustment to MyISAM recovery function
SQL statement and how to handle it.

debian/additions/debian-start.inc.sh

@@ -3,7 +3,7 @@
 # This file is included by /etc/mysql/debian-start
 #
 
-## Check MyISAM and Aria unclosed tables.
+## Is there MyISAM or Aria unclosed tables.
 # - Requires the server to be up.
 # - Is supposed to run silently in background.
 function check_for_crashed_tables() {
@@ -31,14 +31,13 @@ function check_for_crashed_tables() {
   # Note that inside single quotes must be quoted with '\'' (to be outside of single quotes).
   set +e
   # The $MARIADB is intentionally used to expand into a command and arguments
-  # shellcheck disable=SC2086
-  LC_ALL=C echo '
+  echo '
     SELECT CONCAT("select count(*) into @discard from '\''", TABLE_SCHEMA, "'\''.'\''", TABLE_NAME, "'\''")
     FROM information_schema.TABLES WHERE TABLE_SCHEMA<>"INFORMATION_SCHEMA" AND TABLE_SCHEMA<>"PERFORMANCE_SCHEMA"
     AND (ENGINE="MyISAM" OR ENGINE="Aria")
     ' | \
-    $MARIADB --skip-column-names --batch | \
-    xargs -i $MARIADB --skip-column-names --silent --batch --force -e "{}" &> "${tempfile}"
+    LC_ALL=C "$MARIADB" --skip-column-names --batch | \
+    xargs --no-run-if-empty -i "$MARIADB" --skip-column-names --silent --batch --force -e "{}" &> "${tempfile}"
   set -e
 
   if [ -s "$tempfile" ]