patch 8.0.0227: crash with ff=dos when first line in file has no CR

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.
diff --git a/src/fileio.c b/src/fileio.c
index 39e356f..9380953 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2251,8 +2251,9 @@
 			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;
 			    }
diff --git a/src/testdir/test_fileformat.vim b/src/testdir/test_fileformat.vim
index de505d3..8dc25f6 100644
--- a/src/testdir/test_fileformat.vim
+++ b/src/testdir/test_fileformat.vim
@@ -17,7 +17,7 @@
 endfunc
 
 func Test_fileformat_autocommand()
-  let filecnt = ["\<CR>", "foobar\<CR>", "eins\<CR>", "\<CR>", "zwei\<CR>", "drei", "vier", "fünf", ""]
+  let filecnt = ["", "foobar\<CR>", "eins\<CR>", "\<CR>", "zwei\<CR>", "drei", "vier", "fünf", ""]
   let ffs = &ffs
   call writefile(filecnt, 'Xfile', 'b')
   au BufReadPre Xfile set ffs=dos ff=dos
diff --git a/src/version.c b/src/version.c
index 7087f64..84dde73 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    227,
+/**/
     226,
 /**/
     225,