doc: mention that reflect.SetMapIndex no longer panics

when deleting from a nil map.  See issue 8051.

LGTM=r
R=golang-codereviews, r, khr
CC=golang-codereviews
https://golang.org/cl/96540051

1 files changed, 1 insertions, 0 deletions

diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index 2cbda3983c..576cbc3984 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -1620,6 +1620,7 @@ func (v Value) SetCap(n int) {
 // SetMapIndex sets the value associated with key in the map v to val.
 // It panics if v's Kind is not Map.
 // If val is the zero Value, SetMapIndex deletes the key from the map.
+// Otherwise if v holds a nil map, SetMapIndex will panic.
 // As in Go, key's value must be assignable to the map's key type,
 // and val's value must be assignable to the map's value type.
 func (v Value) SetMapIndex(key, val Value) {