OceanPlanarReflection does not initialize properly, when oceanrenderer is not present

**Describe the bug**
Problem is, when crest gets instanciated later, not during startup.

**To Reproduce**
disable oceanrenderer - start - enable oceanrenderer

** Solution **
move some code from Start to OnEnable


**Additional context**
I am using different ocean systems to be compatible on opengl <3.1 and low end devices.