Reason for imgui_impl_sdlrenderer2.cpp line 71 IM_ASSERT(renderer != nullptr && "SDL_Renderer not initialized!")

[AeroSW]

The title of this question is essentially my question. I do not understand what is going wrong with my app when this error occurs. I can't tell if "SDL_Renderer not initialized" is the exception message, or something else. The message also doesn't make sense to me due to the renderer not being null, but it still also not being initialized.

Could I receive clarification on what this line is actually checking? I would like to know, so I can effectively debug my engine.