Allow the modification on FcTypeVoid with FcTypeLangSet and FcTypeCharSet

FcTypeVoid is likely to happen when 'lang' and 'charset'
is deleted by 'delete' or 'delete_all' mode in edit.
Without this change, any modification on them are simply
ignored.

This is useful to make a lot of changes, particularly
when one wants to add a few and delete a lot say.

src/fccfg.c

@@ -722,6 +722,16 @@ FcConfigPromote (FcValue v, FcValue u, FcValuePromotionBuffer *buf)
 	v.u.l = FcLangSetPromote (v.u.s, buf);
 	v.type = FcTypeLangSet;
     }
+    else if (v.type == FcTypeVoid && u.type == FcTypeLangSet)
+    {
+	v.u.l = FcLangSetPromote (NULL, buf);
+	v.type = FcTypeLangSet;
+    }
+    else if (v.type == FcTypeVoid && u.type == FcTypeCharSet)
+    {
+	v.u.c = FcCharSetPromote (buf);
+	v.type = FcTypeCharSet;
+    }
     if (buf && v.type == FcTypeDouble && u.type == FcTypeRange)
     {
 	v.u.r = FcRangePromote (v.u.d, buf);

src/fccharset.c

@@ -42,6 +42,21 @@ FcCharSetCreate (void)
     return fcs;
 }
 
+FcCharSet *
+FcCharSetPromote (FcValuePromotionBuffer *vbuf)
+{
+    FcCharSet *fcs = (FcCharSet *) vbuf;
+
+    FC_ASSERT_STATIC (sizeof (FcCharSet) <= sizeof (FcValuePromotionBuffer));
+
+    FcRefSetConst (&fcs->ref);
+    fcs->num = 0;
+    fcs->leaves_offset = 0;
+    fcs->numbers_offset = 0;
+
+    return fcs;
+}
+
 FcCharSet *
 FcCharSetNew (void)
 {

src/fcint.h

@@ -720,6 +720,9 @@ FcPrivate FcLangSet *
 FcLangSetSerialize(FcSerialize *serialize, const FcLangSet *l);
 
 /* fccharset.c */
+FcPrivate FcCharSet *
+FcCharSetPromote (FcValuePromotionBuffer *vbuf);
+
 FcPrivate void
 FcLangCharSetPopulate (void);
 

src/fclang.c

@@ -720,6 +720,8 @@ FcLangSetPromote (const FcChar8 *lang, FcValuePromotionBuffer *vbuf)
     memset (buf->ls.map, '\0', sizeof (buf->ls.map));
     buf->ls.map_size = NUM_LANG_SET_MAP;
     buf->ls.extra = 0;
+    if (lang)
+    {
 	id = FcLangSetIndex (lang);
 	if (id > 0)
 	{
@@ -734,6 +736,7 @@ FcLangSetPromote (const FcChar8 *lang, FcValuePromotionBuffer *vbuf)
 	    FcRefInit (&buf->strs.ref, 1);
 	    buf->str = (FcChar8 *) lang;
 	}
+    }
     return &buf->ls;
 }