Fix various uninitialized member pointers

Using this command:
```
find -name "thirdparty" -prune -o -name "*.h" -exec sed -i {} -e '/return /! s/\t\([A-Za-z0-9_]* \*[A-Za-z0-9_]*\)\;/\t\1 = nullptr;/g' \;
```

And then reviewing the changes manually to discard the ones that don't
seem correct/safe/good (notably changes to `core` unions).

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gles3/rasterizer_scene_gles3.h b/drivers/gles3/rasterizer_scene_gles3.h
index 04658b10ad..881fc5615c 100644
--- a/drivers/gles3/rasterizer_scene_gles3.h
+++ b/drivers/gles3/rasterizer_scene_gles3.h
@@ -597,7 +597,7 @@ protected:
 public:
 	static RasterizerSceneGLES3 *get_singleton() { return singleton; }
 
-	RasterizerCanvasGLES3 *canvas;
+	RasterizerCanvasGLES3 *canvas = nullptr;
 
 	RenderGeometryInstance *geometry_instance_create(RID p_base) override;
 	void geometry_instance_free(RenderGeometryInstance *p_geometry_instance) override;