base-files: config_get: prevent filename globbing

When config_get is called as "config_get section option" the option
is unexpectedly globbed by the shell which differs from the way options
are read to a variable with "config_get variable section option".
Add another layer of double quotes to fix it.

Signed-off-by: Günther Kelleter <guenther.kelleter@devolo.de>
(backported from commit c3389ab135)

package/base-files/files/lib/functions.sh

@@ -92,7 +92,7 @@ config_unset() {
 # config_get <section> <option>
 config_get() {
 	case "$3" in
-		"") eval echo "\${CONFIG_${1}_${2}:-\${4}}";;
+		"") eval echo "\"\${CONFIG_${1}_${2}:-\${4}}\"";;
 		*)  eval export ${NO_EXPORT:+-n} -- "${1}=\${CONFIG_${2}_${3}:-\${4}}";;
 	esac
 }