DOC: Add whatsnew note

Licht-T · Licht-T · commit 0b71ffee5626 · 2017-11-25T22:57:01.000+09:00
diff --git a/doc/source/whatsnew/v0.21.1.txt b/doc/source/whatsnew/v0.21.1.txt
@@ -75,7 +75,7 @@ Indexing
 
 - Bug in a boolean comparison of a ``datetime.datetime`` and a ``datetime64[ns]`` dtype Series (:issue:`17965`)
 - Bug where a ``MultiIndex`` with more than a million records was not raising ``AttributeError`` when trying to access a missing attribute (:issue:`18165`)
--
+- Bug in ``Index.putmask`` when an invalid mask passed (:issue:`18368`)
 -
 
 I/O

Original file line number	Diff line number	Diff line change
`@@ -75,7 +75,7 @@ Indexing`
`75`	`75`
`76`	`76`	- Bug in a boolean comparison of a ``datetime.datetime`` and a ``datetime64[ns]`` dtype Series (:issue:`17965`)
`77`	`77`	- Bug where a ``MultiIndex`` with more than a million records was not raising ``AttributeError`` when trying to access a missing attribute (:issue:`18165`)
`78`		`--`
	`78`	+- Bug in ``Index.putmask`` when an invalid mask passed (:issue:`18368`)
`79`	`79`	`-`
`80`	`80`
`81`	`81`	`I/O`