* lisp/minibuffer.el (minibuffer-force-complete-and-exit): Use
base size as determined by 'completion-all-sorted-completions',
instead of the beginning of current completion field (from
'completion-boundaries'). Those can differ when
'partial-completion' picks up part of the previous fields. For
example, in file name completion with input "emacs/lisp/pr/xr",
we want to replace also the last field "pr" when completing to
"emacs/lisp/progmodes/xref.el".