when i use sal services, even the required action is done well, http status 500 is returned

odl:http://nexus.opendaylight.org/content/repositories/opendaylight.snapshot/org/opendaylight/integration/distribution-karaf/0.3.0-SNAPSHOT//distribution-karaf-0.3.0-20150312.085342-602.tar.gz

used default settings (heap, perm size)

installed feature: odl-openflowplugin-all

host VM: fedora 18 with 16G of ram

java -version
java version "1.7.0_67"
Java(TM) SE Runtime Environment (build 1.7.0_67-b01)
Java HotSpot(TM) 64-Bit Server VM (build 24.65-b04, mixed mode)

used data:
POST on /restconf/operations/sal-flow:add-flow

used xml:
<input xmlns="urn:opendaylight:flow:service"> <strict>false</strict> <instructions> <instruction> <order>0</order> <apply-actions> <action> <order>0</order> <dec-nw-ttl /> </action> </apply-actions> </instruction> </instructions> <table_id>2</table_id> <cookie_mask>255</cookie_mask> <installHw>false</installHw> <match> <ethernet-match> <ethernet-type> <type>2048</type> </ethernet-type> </ethernet-match> <ipv4-destination>10.0.1.0/24</ipv4-destination> </match> <cookie>1</cookie> <flow-name>FooXf1</flow-name> <priority>1</priority> <barrier>false</barrier> <node xmlns:inv="urn:opendaylight:inventory">/inv:nodes/inv:node[inv:id="openflow:1"]</node></input>

switch:
OFPST_FLOW reply (OF1.3) (xid=0x2): cookie=0x1, duration=30.104s, table=2, n_packets=0, n_bytes=0, idle_timeout=300, hard_timeout=600, priority=1,ip,nw_dst=10.0.1.0/24 actions=dec_ttl mininet>

but http 500 returned