Got rid of segfault when uploading VBOs.

Added go-to-zero function.
Reworked how work pos is obtained.

render.h

@@ -27,6 +27,7 @@ private:
     GLuint vbo_id;
     GLuint vao_id;
 
+    std::vector<float> buffer_data;
     shader_program *shader = nullptr;
 
     bool initialized = false;