patch 8.2.4478: crash when using fuzzy completion

Problem:    Crash when using fuzzy completion.
Solution:   Temporary fix: put back regexp. (closes #9852, closes #9851)

src/cmdexpand.c

@@ -2496,6 +2496,8 @@ ExpandFromContext(
     int		ret;
     int		flags;
     char_u	*tofree = NULL;
+    int		fuzzy = cmdline_fuzzy_complete(pat)
+				     && cmdline_fuzzy_completion_supported(xp);
 
     flags = map_wildopts_to_ewflags(options);
 
@@ -2580,12 +2582,15 @@ ExpandFromContext(
 	pat = tofree;
     }
 
+    if (!fuzzy)
+    {
 	regmatch.regprog = vim_regcomp(pat, magic_isset() ? RE_MAGIC : 0);
 	if (regmatch.regprog == NULL)
 	    return FAIL;
 
 	// set ignore-case according to p_ic, p_scs and pat
 	regmatch.rm_ic = ignorecase(pat);
+    }
 
     if (xp->xp_context == EXPAND_SETTINGS
 	    || xp->xp_context == EXPAND_BOOL_SETTINGS)
@@ -2599,6 +2604,7 @@ ExpandFromContext(
     else
 	ret = ExpandOther(pat, xp, &regmatch, matches, numMatches);
 
+    if (!fuzzy)
 	vim_regfree(regmatch.regprog);
     vim_free(tofree);
 

src/testdir/test_cmdline.vim

@@ -2659,6 +2659,10 @@ func Test_wildoptions_fuzzy()
   call assert_equal('"mapclear <buffer>', @:)
 
   " map name fuzzy completion - NOT supported
+  " test regex completion works
+  set wildoptions=fuzzy
+  call feedkeys(":cnoremap <ex\<Tab> <esc> \<Tab>\<C-B>\"\<CR>", 'tx')
+  call assert_equal("\"cnoremap <expr> <esc> \<Tab>", @:)
 
   " menu name fuzzy completion
   if has('gui_running')

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4478,
 /**/
     4477,
 /**/