Setting a Refresh value of 0 on a RenderTargetWidget will cause the workspace to crash with a div0 error
Default Layout widget values for RenderTargetWidget are:
Camera: 0
Refresh: 0
Offset: -1
This indicates that Refresh can support a value of 0, even if it functions as if having a value of 1
The tooltip for the Refresh Attribute says:
Limit refresh to n-th frame (min=0, max=255)
Code hint for RenderTargetWidget.SetRefresh() says:
//!when period > 1 then every n-th frame will be rendered. Offset is initial counter. proto external void SetRefresh(int period, int offset);
This would indicate (to me) that any period below 2 will skip no frames, or at least safely clamp period values to >= 1