The "ale#handlers#sh#GetShellType()" function currently falls back
to the file type without checking for buffer-local variables first.
This causes the function to return "sh" even when a script is known
by Vim to be a script of a more specific type (e.g., "bash").
The "ale#handlers#shellcheck#GetDialectArgument()" function then
erroneously uses this type even though a more fitting type should be
used instead. Files without a "#!" line will be of type "sh" even
though they may have a ".bash" suffix.
This commit fixes the problem by checking for buffer-local shell
type variables (set by Vim) before falling back to the file type.
Jason Franklin