+format-region-p = nil

Should be a boolean in the first place; this fixes custom formatters
that use it like a boolean.

modules/editor/format/autoload/format.el

@@ -1,8 +1,8 @@
 ;;; editor/format/autoload.el -*- lexical-binding: t; -*-
 
-(defvar +format-region-p 'buffer
-  "A symbol representing whether the buffer or a region of it is being
-formatted. Can be 'buffer or 'region.")
+(defvar +format-region-p nil
+  "Is non-nil if currently reformatting a selected region, rather than the whole
+buffer.")
 
 ;;;###autoload
 (autoload 'format-all-probe "format-all")