scripts/env: fix remaining shellcheck warning

Fixes following shellcheck warning:

 In scripts/env line 25:
 	exit ${1:-1}
             ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Signed-off-by: Petr Štetiar <[email protected]>

scripts/env

@@ -22,7 +22,7 @@ Commands:
 Options:
 
 EOF
-	exit ${1:-1}
+	exit "${1:-1}"
 }
 
 error() {