Attempt at combining nanovg and SDL2. Getting 'Error 00000500 after init' after creating the GL3 context in nanovg. Any ideas what's happening here?

nanovg_sdl2.c

#include <stdio.h>
#include <stdlib.h>

#include <GL/glew.h>

#include <SDL2/SDL.h>

#include "nanovg.h"
#define NANOVG_GL3_IMPLEMENTATION
#include "nanovg_gl.h"
#include "nanovg_gl_utils.h"

int sdl_init( SDL_Window **w );
void sdl_cleanup();

int main( int argc, char *argv[] )
{
  SDL_Window *window = NULL;

  if ( sdl_init( &window ) != 0 )
  {
    // Report SDL's error
    printf( "Couldn't init SDL: %s\n", SDL_GetError() );
    return 1;
  }

  struct NVGcontext *vg = NULL;
  struct NVGLUframebuffer *fb = NULL;

  printf( "Creating nanovg context\n" );
  vg = nvgCreateGL3( 512, 512, NVG_ANTIALIAS|NVG_STENCIL_STROKES );
  if ( !vg )
  {
    printf( "Couldn't create nanovg gl3 context\n" );
    // Couldn't create context
    sdl_cleanup();
    return 2;
  }

  printf( "Creating nanovg framebuffer\n" );
  fb = nvgluCreateFramebuffer( vg, 600, 600 );
  if ( !fb )
  {
    // Couldn't create framebuffer
    printf( "Couldn't create nanovg framebuffer\n" );
    sdl_cleanup();
    return 3;
  }
  printf( "Nanovg initialized!\n" );

  int quit = 0;

  float angle = 0.0f;

  while ( quit == 0 )
  {

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);

    nvgBeginFrame( vg, 800, 600, pxRatio, NVG_STRAIGHT_ALPHA );

    nvgResetTransform( vg );
    
    nvgTranslate( vg, 300.0f, 300.0f );
    //angle = fmod( angle + 0.1f, 360.0f );
    //nvgRotate( vg, angle );
    
    nvgBeginPath( vg );
    nvgRect( vg, -100, -25, 200, 50 );
    nvgStrokeColor( vg, nvgRGBA( 255, 0, 0, 100 ) );
    nvgStrokeWidth( vg, 1.0f );
    nvgStroke( vg );

    nvgEndFrame( vg );
    nvgluBindFramebuffer( NULL );

    SDL_Event e;
    while ( SDL_PollEvent( &e ) )
    {
      switch( e.type )
      {
      case SDL_KEYDOWN:
      case SDL_KEYUP:
        break;
      case SDL_MOUSEBUTTONDOWN:
      case SDL_MOUSEBUTTONUP:
        break;
      case SDL_MOUSEMOTION:
        break;
      case SDL_MOUSEWHEEL:
        break;
      case SDL_QUIT:
        quit = 1;
        break;
      }
    }

    SDL_GL_SwapWindow( window );
  }


  nvgluDeleteFramebuffer( vg, fb );
  nvgDeleteGL3( vg );

  sdl_cleanup();

  return 0;
}

int sdl_init( SDL_Window **w )
{
  if ( SDL_Init( SDL_INIT_TIMER | SDL_INIT_VIDEO | SDL_INIT_GAMECONTROLLER | SDL_INIT_EVENTS ) == 0 )
  {
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 3 );
    //SDL_GL_SetAttribute( SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG ); // May be a performance booster in *nix?
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE );
    SDL_GL_SetAttribute( SDL_GL_STENCIL_SIZE, 8 );

    *w = SDL_CreateWindow( "Mayhem v3", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 1024, 768, SDL_WINDOW_OPENGL );
    if ( *w )
    {
      SDL_GL_CreateContext( *w );

      // Activate glew
      glewExperimental = GL_TRUE;
      GLenum err = glewInit();
      if ( err == GLEW_OK )
      {
        glEnable(GL_STENCIL_TEST);

        return 0;
      }
      else
      {
        // Send GLEW error as an SDL Error
        // SDL's error should be clear, since any previous error would stop further initialization
        SDL_SetError( "GLEW Reported an Error: %s", glewGetErrorString(err) );
      }
    }
  }
  if ( *w ) SDL_DestroyWindow( *w );
  *w = NULL;
  return 1;
}

void sdl_cleanup()
{
  SDL_Quit();
}