fixed crash when setting heightfield's scale before the heightfield's texture
fixed crash when setting heightfield's scale before the heightfield's texture

JakubLukas/LumixEngine,JakubLukas/LumixEngine,zhouxh1023/LumixEngine,galek/LumixEngine,dreamsxin/LuxEngine,gamedevforks/LumixEngine,zhouxh1023/LumixEngine,dreamsxin/LuxEngine,galek/LumixEngine,gamedevforks/LumixEngine,JakubLukas/LumixEngine