Check if EffectImplemented::Create() returns nullptr. (#686)
Check if EffectImplemented::Create() returns nullptr. (#686)

If you try to load an effect file that exists but contains bad data,
EffectImplemented::Create() will return a nullptr. Attempting to use
this later in the function with effect->SetName() causes a segmentation
fault.
effekseer/Effekseer,effekseer/Effekseer,effekseer/Effekseer,effekseer/Effekseer,effekseer/Effekseer,effekseer/Effekseer,effekseer/Effekseer