Here Joseph Smith, in his editing for the 1837 edition, emended the nonstandard “ye was” to “ye were”. This is the only example of “ye was” in the earliest text; in all other instances, the text reads “ye were” (20 times). Obviously, this nonstandard reading may be due to some kind of dialectal overlay (an instance of nonstandard English that entered the text early on in its transmission). A similar example, also fairly rare, is the case of “they was” that occurs as the earliest reading in several passages. As discussed under 1 Nephi 4:4 and Mosiah 10:14, the critical text will allow some instances of “they was” to stand. Further, there is at least one instance in the earliest text where one of the associated verbs for ye takes the inflectional ending -(e)th: “and yet ye put up no petition or repenteth not of the thing which thou hast done” (Mosiah 4:22). The critical text will accept these rare instances of nonstandard verb agreement for ye since they are dialectally possible and may actually be intended.
Summary: Restore the original nonstandard “ye was” in Alma 7:17; another example of nonstandard subject-verb agreement involving ye is found in Mosiah 4:22: “and yet ye put up no petition or repenteth not of the thing which thou hast done”.