The 1837 typesetter seems to have accidentally misread also as all. Both manuscripts have also, as well as the 1830 edition. Either reading will work here, so we follow the reading of the earliest textual sources. The phrase “and also” is very common in the Book of Mormon text.
Summary: Restore also for all in Alma 47:34: “and also they which were with him” (the reading of the earliest textual sources).