patch 8.2.3112: in rare cases the cursor may be somewhere in a folded line

patch 8.2.3112: in rare cases the cursor may be somewhere in a folded line

Problem:    With concealing enabled and indirectly closing a fold the cursor
            may be somewhere in a folded line when it is not on the first line
            of the fold.
Solution:   Check if he cursor is somewhere in the folded text.