Fixup ttx file-name mangling after eac107f1
diff --git a/Lib/fontTools/ttx.py b/Lib/fontTools/ttx.py
index 56f211a..d649c38 100644
--- a/Lib/fontTools/ttx.py
+++ b/Lib/fontTools/ttx.py
@@ -90,9 +90,9 @@
 	if outputDir:
 		dir = outputDir
 	output = os.path.join(dir, file + extension)
-	m = numberAddedRE.search(file)
-	if m:
-		file = m.group(1)
+	m = numberAddedRE.split(file)
+	if len(m) > 1:
+		file = m[0]
 	n = 1
 	while os.path.exists(output):
 		output = os.path.join(dir, file + "#" + repr(n) + extension)