Fix tonemap palette not being rebuilt on palette change

src/gl/renderer/gl_postprocess.cpp

@@ -278,6 +278,12 @@ void FGLRenderer::BindTonemapPalette(int texunit)
 	}
 }
 
+void FGLRenderer::ClearTonemapPalette()
+{
+	delete mTonemapPalette;
+	mTonemapPalette = nullptr;
+}
+
 //-----------------------------------------------------------------------------
 //
 // Apply lens distortion and place the result in the HUD/2D texture

src/gl/renderer/gl_renderer.cpp

@@ -111,6 +111,7 @@ FGLRenderer::FGLRenderer(OpenGLFrameBuffer *fb)
 	gllight = glpart2 = glpart = mirrortexture = NULL;
 	mLights = NULL;
 	m2DDrawer = nullptr;
+	mTonemapPalette = nullptr;
 }
 
 void gl_LoadModels();

src/gl/renderer/gl_renderer.h

@@ -167,6 +167,7 @@ public:
 	void BloomScene();
 	void TonemapScene();
 	void BindTonemapPalette(int texunit);
+	void ClearTonemapPalette();
 	void LensDistortScene();
 	void CopyToBackbuffer(const GL_IRECT *bounds, bool applyGamma);
 	void Flush() { CopyToBackbuffer(nullptr, true); }

src/gl/system/gl_framebuffer.cpp

@@ -310,6 +310,9 @@ void OpenGLFrameBuffer::UpdatePalette()
 	bb>>=8;
 
 	palette_brightness = (rr*77 + gg*143 + bb*35)/255;
+
+	if (GLRenderer)
+		GLRenderer->ClearTonemapPalette();
 }
 
 void OpenGLFrameBuffer::GetFlashedPalette (PalEntry pal[256])