enable garbage collection for pdfpage and ft_face

ft.c

@@ -140,9 +140,12 @@ static int renderGlyph(lua_State *L) {
 
 static int doneFace(lua_State *L) {
 	FT_Face *face = (FT_Face*) luaL_checkudata(L, 1, "ft_face");
-	FT_Error error = FT_Done_Face(*face);
-	if(error) {
-		return luaL_error(L, "freetype error when freeing face");
+	if(*face != NULL) {
+		FT_Error error = FT_Done_Face(*face);
+		if(error) {
+			return luaL_error(L, "freetype error when freeing face");
+		}
+		*face = NULL;
 	}
 	return 0;
 }
@@ -150,6 +153,7 @@ static int doneFace(lua_State *L) {
 static const struct luaL_reg ft_face_meth[] = {
 	{"renderGlyph", renderGlyph},
 	{"done", doneFace},
+	{"__gc", doneFace},
 	{NULL, NULL}
 };
 

pdf.c

@@ -231,9 +231,12 @@ static int closePage(lua_State *L) {
 #endif
 	//fz_free_glyph_cache(page->doc->glyphcache);
 	//page->doc->glyphcache = fz_new_glyph_cache();
-	pdf_free_page(page->page);
+	if(page->page != NULL) {
+		pdf_free_page(page->page);
 
-	pdf_age_store(page->doc->xref->store, 2);
+		pdf_age_store(page->doc->xref->store, 2);
+		page->page = NULL;
+	}
 }
 
 static int drawPage(lua_State *L) {
@@ -315,6 +318,7 @@ static const struct luaL_reg pdfpage_meth[] = {
 	{"getSize", getPageSize},
 	{"getUsedBBox", getUsedBBox},
 	{"close", closePage},
+	{"__gc", closePage},
 	{"draw", drawPage},
 	{NULL, NULL}
 };