patch 8.2.4418: crash when using special multi-byte character

Problem:    Crash when using special multi-byte character.
Solution:   Don't use isalpha() for an arbitrary character.

src/charset.c

@@ -1644,6 +1644,12 @@ vim_isupper(int c)
     return isupper(c);
 }
 
+    int
+vim_isalpha(int c)
+{
+    return vim_islower(c) || vim_isupper(c);
+}
+
     int
 vim_toupper(int c)
 {

src/filepath.c

@@ -3626,7 +3626,7 @@ unix_expandpath(
 	else if (path_end >= path + wildoff
 			 && (vim_strchr((char_u *)"*?[{~$", *path_end) != NULL
 			     || (!p_fic && (flags & EW_ICASE)
-					     && isalpha(PTR2CHAR(path_end)))))
+					  && vim_isalpha(PTR2CHAR(path_end)))))
 	    e = p;
 	if (has_mbyte)
 	{

src/proto/charset.pro

@@ -50,6 +50,7 @@ int vim_isxdigit(int c);
 int vim_isbdigit(int c);
 int vim_islower(int c);
 int vim_isupper(int c);
+int vim_isalpha(int c);
 int vim_toupper(int c);
 int vim_tolower(int c);
 char_u *skiptowhite(char_u *p);
@@ -63,5 +64,4 @@ int hexhex2nr(char_u *p);
 int rem_backslash(char_u *str);
 void backslash_halve(char_u *p);
 char_u *backslash_halve_save(char_u *p);
-void ebcdic2ascii(char_u *buffer, int len);
 /* vim: set ft=c : */

src/testdir/test_autochdir.vim

@@ -110,4 +110,12 @@ func Test_verbose_pwd()
   call delete('Xautodir', 'rf')
 endfunc
 
+func Test_multibyte()
+  " using an invalid character should not cause a crash
+  set wic
+  call assert_fails('tc <20><><EFBFBD><EFBFBD><EFBFBD>*', 'E344:')
+  set nowic
+endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4418,
 /**/
     4417,
 /**/