Improve docs of optional indexing syntax to make it clear (ref #2588) (#2604)

* Revert "Typo in basic filters manual (#2588)"

This reverts commit 908f5d54a7.

* Improve docs of optional indexing syntax to make it clear

docs/content/manual/v1.5/manual.yml

@@ -297,8 +297,8 @@ sections:
       - title: "`.foo?`"
         body: |
 
-          Just like `.foo`, but does not output even an error when `.`
-          is not an array or an object.
+          Just like `.foo`, but does not output an error when `.` is not an
+          object.
 
         examples:
           - program: '.foo?'