ubus: update to latest git HEAD

884be45 libubus: check for non-NULL data before running callbacks

Signed-off-by: John Crispin <john@phrozen.org>

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:=2018-01-16
-PKG_SOURCE_VERSION:=5bae22eb5472c9c7cc30caa9a84004bba19940d3
-PKG_MIRROR_HASH:=6f46398279339dcc597965306275fe1272af384f8cb253ee8de2c68e366eed55
+PKG_SOURCE_DATE:=2018-07-25
+PKG_SOURCE_VERSION:=884be451622d21fe3a7b06cc5b9d245bc4fffbf2
+PKG_MIRROR_HASH:=4f4bceade7f4027bc1d813c7f6810eabe514a04dfb470e6d48918b79dfdf847f
 CMAKE_INSTALL:=1
 
 PKG_LICENSE:=LGPL-2.1