Segmentation fault when transposing a char

```jl
julia> c = '1'
'1': ASCII/Unicode U+0031 (category Nd: Number, decimal digit)

julia> c'

signal (11): Segmentation fault: 11
in expression starting at no file:0
unknown function (ip: 0xffffffffffffffff)
Allocations: 3423488 (Pool: 3422945; Big: 543); GC: 6
```