fix iobber when no disamb_only input

iobber/corpio.py

@@ -55,8 +55,9 @@ def get_reader(in_path, tagset, input_format, read_disamb_only):
 	"""Creates a reader using the options. If in_path evaluates to False,
 	will create a stdin reader. Set read_disamb_only to force reading only
 	'disamb' lexemes/interpretations."""
+	fixd_format = input_format
 	if read_disamb_only:
-		fixd_format = input_format + ',disamb_only'
+		fixd_format += ',disamb_only'
 	# force casting sentences as AnnotatedSentences
 	# required to get XCES input right
 	fixd_format += ',ann'