patch 8.2.4563: "z=" in Visual mode may go beyond the end of the line

Problem:    "z=" in Visual mode may go beyond the end of the line.
Solution:   Adjust "badlen".

src/spellsuggest.c

@@ -506,6 +506,10 @@ spell_suggest(int count)
 	    curwin->w_cursor.col = VIsual.col;
 	++badlen;
 	end_visual_mode();
+	// make sure we don't include the NUL at the end of the line
+	line = ml_get_curline();
+	if (badlen > STRLEN(line) - curwin->w_cursor.col)
+	    badlen = STRLEN(line) - curwin->w_cursor.col;
     }
     // Find the start of the badly spelled word.
     else if (spell_move_to(curwin, FORWARD, TRUE, TRUE, NULL) == 0

src/testdir/test_spell.vim

@@ -456,6 +456,21 @@ func Test_spellsuggest_timeout()
   call assert_fails('set spellsuggest=timeout:--9', 'E474:')
 endfunc
 
+func Test_spellsuggest_visual_end_of_line()
+  let enc_save = &encoding
+  set encoding=iso8859
+
+  " This was reading beyond the end of the line.
+  norm R00000000000
+  sil norm 0
+  sil! norm i00000)
+  sil! norm i00000)
+  call feedkeys("\<CR>")
+  norm z=
+
+  let &encoding = enc_save
+endfunc
+
 func Test_spellinfo()
   new
   let runtime = substitute($VIMRUNTIME, '\\', '/', 'g')

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4563,
 /**/
     4562,
 /**/