Here the 1874 RLDS edition and the 1920 LDS edition changed the singular “there was none” to the plural “there were none”. The 1908 RLDS edition restored the original was to the RLDS text, but the LDS text has continued with the secondary were.
The Book of Mormon text has examples of the subject none taking singular and plural verb forms, as in these examples where either could occur:
(The first two of these are quotes from Isaiah; the phrase in Mormon 5:24, “there is none to deliver”, is biblically styled, as in Psalm 7:2 and Psalm 71:11.) The grammatical number has not been changed in any of these cases (although in Ether 4:3 Joseph Smith momentarily changed the is to are in 𝓟 in his editing for the 1837 edition, but then he changed his mind and restored the singular is in 𝓟). Thus the critical text will in each case of subject none follow the number of the verb in the earliest reading. Hence here in Ether 13:17, the original was will be restored.
Summary: Restore the original singular was in Ether 13:17, “there was none of the fair sons and daughters upon the face of the whole earth which repented of their sins”.