[PATCH] Remove redundant path_nulls checks in setPathObject/Array

Hi all,

I noticed redundant path_nulls checks in setPathObject and setPathArray,
so here's a small refactoring patch to remove them.

- Both checks were introduced in c694701 (12 May 2015, "Additional
functions and operators for jsonb") with the functions' initial code.

- Both functions always had a single call site, `setPath`, as they are
internal implementations for the two cases (array/object) in a generic
function.

- Later, in 1edd4ec (4 Oct 2015, "Disallow invalid path elements in
jsonb_set"), the path_nulls check was propagated into setPath itself.

If desired, those conditions can be transformed into Assert()s with a
comment about setPath() validation.

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Ilya Gladyshev // foxido.dev