This is a good example of using aleph as a symbol of an open syllable and therefore as a semi vowel. The later editors rarely did this, if ever. This is discussed below under variations which see. M has 'adonay. Hence the dark stroke in the word.
Aramaic influence is the most probable reason.
A waw is also edited above the line after kaph. Since this is not ordinarily done it may have been the original scribe. See above under Additions to the text.