vim-patch:8.0.0227 (#7548)

Problem:    Crash when 'fileformat' is forced to "dos" and the first line in
            the file is empty and does not have a CR character.
Solution:   Don't check for CR before the start of the buffer.

2aa5f696b9

src/nvim/fileio.c

@@ -1622,7 +1622,8 @@ rewind_retry:
             *ptr = NUL;                         /* end of line */
             len = (colnr_T)(ptr - line_start + 1);
             if (fileformat == EOL_DOS) {
-              if (ptr[-1] == CAR) {             /* remove CR */
+              if (ptr > line_start && ptr[-1] == CAR) {
+                // remove CR before NL
                 ptr[-1] = NUL;
                 len--;
               } else if (ff_error != EOL_DOS) {