set _node to null in createNodeWithSceneFile

_node was being set to null only in constructor, so when we call method createNodeWithSceneFile with path to existing file and then call it again with path to missing file (not calling destroyInstance method), it returns a pointer to previously created node, what may lead to a crash.
fix compiler error in wp8
Merge pull request #6215 from samuele3hu/develop_fix

update config files for lua bindings-generator and `lua_cocos2dx_manual.cpp` file
Fixed logical error in CameraCenterTest::onExit.
Merge pull request #6216 from Dhilan007/develop

Fixed logical error in CameraCenterTest::onExit.
Update CHANGELOG [ci skip]
[AUTO]: updating luabinding automatically
Merge pull request #6217 from CocosRobot/update_lua_bindings_1397117948

[AUTO]: updating luabinding automatically
[AUTO]: updating luabinding automatically
Merge pull request #6218 from CocosRobot/update_lua_bindings_1397118502

[AUTO]: updating luabinding automatically
[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #6219 from CocosRobot/update_cocosfiles_1397119257

[AUTO][ci skip]: updating cocos2dx_files.json
Fixed logical error in TestChangeAnimationInternal::onExit.
replace LabelTTF with Label
Merge pull request #6220 from Dhilan007/develop

Fixed logical error in TestChangeAnimationInternal::onExit.
Merge pull request #6123 from ololomax/patch-1

set _node to null in createNodeWithSceneFile
Update AUTHORS [ci skip]
Merge pull request #6213 from koowolf/wp8_fix

fix compiler error in wp8
Update CHANGELOG [ci skip]
Removed unused comments in GUIDefine.h