patch 8.2.1926: cannot use a space in 'spellfile'

Problem:    Cannot use a space in 'spellfile'. (Filipe Brandenburger)
Solution:   Permit using a space. (closes #7230)
diff --git a/src/spell.c b/src/spell.c
index 085f317..b474a38 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -4340,7 +4340,7 @@
     char_u *s;
 
     for (s = val; *s != NUL; ++s)
-	if (!vim_isfilec(*s) && *s != ',')
+	if (!vim_isfilec(*s) && *s != ',' && *s != ' ')
 	    return FALSE;
     return TRUE;
 }