patch 8.0.1225: no check for spell region being zero

Problem:    No check for spell region being zero. (geeknik)
Solution:   Check for zero. (closes #2252)

src/spellfile.c

@@ -4277,7 +4277,7 @@ spell_read_wordfile(spellinfo_T *spin, char_u *fname)
 		    flags |= WF_REGION;
 
 		    l = *p - '0';
-		    if (l > spin->si_region_count)
+		    if (l == 0 || l > spin->si_region_count)
 		    {
 			smsg((char_u *)_("Invalid region nr in %s line %d: %s"),
 							  fname, lnum, p);

src/testdir/test_spell.vim

@@ -271,6 +271,15 @@ func Test_zz_sal_and_addition()
   call assert_equal("elekwint", SecondSpellWord())
 endfunc
 
+func Test_region_error()
+  messages clear
+  call writefile(["/regions=usgbnz", "elequint/0"], "Xtest.latin1.add")
+  mkspell! Xtest.latin1.add.spl Xtest.latin1.add
+  call assert_match('Invalid region nr in Xtest.latin1.add line 2: 0', execute('messages'))
+  call delete('Xtest.latin1.add')
+  call delete('Xtest.latin1.add.spl')
+endfunc
+
 " Check using z= in new buffer (crash fixed by patch 7.4a.028).
 func Test_zeq_crash()
   new

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1225,
 /**/
     1224,
 /**/