Validates texture in set_piece_texture

scene/resources/texture.cpp

@@ -1333,6 +1333,7 @@ void LargeTexture::set_piece_offset(int p_idx, const Point2 &p_offset) {
 void LargeTexture::set_piece_texture(int p_idx, const Ref<Texture> &p_texture) {
 
 	ERR_FAIL_COND(p_texture == this);
+	ERR_FAIL_COND(p_texture.is_null());
 	ERR_FAIL_INDEX(p_idx, pieces.size());
 	pieces.write[p_idx].texture = p_texture;
 };