This commit fixes two related things:

1. If the loop goes all the way through the slice without a match, on
   the last iteration `mid == symbols.len - 1` which causes
   `&symbols[mid + 1]` to be out of bounds. End one step before that
   instead.

2. If the address we're looking for is greater than the address of the
   last symbol in the slice, we now match it to that symbol. Previously,
   we would miss this case since we only matched if the address was _in
   between_ the address of two symbols.