Potential undefined array access in XML-RPC mw_newPost/mw_editPost

[maxcutler]

When attempting to determine the appropriate cap check, some of the logic attempts to access members of the content_struct array that are not required to be set, resulting in 'undefined index' error/notice.

Specifically, this can occur when 'post_type' is supplied but not 'post_status'.

An example XML-RPC request that triggers one of the two if statements is in the test_call.txt attachment.

[maxcutler]

Discovered that the same logic was copy/pasted to mw_editPost, so patching that as well.

[westi]

In [20323]:

XMLRPC: In mw_newPost check to see if the post_status has been supplied before trying to use it to avoid undefined array access notices. Fixes #19774 props maxcutler.