Drop format=0 cmap subtables
diff --git a/pyotlss.py b/pyotlss.py
index c8bb2ee..e09f94d 100755
--- a/pyotlss.py
+++ b/pyotlss.py
@@ -383,6 +383,8 @@
 		else:
 			t.cmap = {u:g for (u,g) in t.cmap.items() if g in glyphs}
 	self.tables = [t for t in self.tables if (t.cmap if t.format != 14 else t.uvsDict)]
+	# Drop format=0 which can't be subset easily?
+	self.tables = [t for t in self.tables if t.format != 0]
 	return len (self.tables)