ubus: update to latest git HEAD

40e0931 libubus: pass an empty UBUS_ATTR_DATA block if msg is NULL on invoke

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/system/ubus/Makefile

@@ -5,9 +5,9 @@ PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/ubus.git
-PKG_SOURCE_DATE:=2018-07-25
-PKG_SOURCE_VERSION:=884be451622d21fe3a7b06cc5b9d245bc4fffbf2
-PKG_MIRROR_HASH:=4f4bceade7f4027bc1d813c7f6810eabe514a04dfb470e6d48918b79dfdf847f
+PKG_SOURCE_DATE:=2018-07-26
+PKG_SOURCE_VERSION:=40e0931e70bfe198690a7dac43b32fad06f46ef9
+PKG_MIRROR_HASH:=ddf8a42ff9a88a81b87058887d79a4eea6f2d606a29f168422d41112702793e5
 CMAKE_INSTALL:=1
 
 PKG_LICENSE:=LGPL-2.1