ERR_FAIL_NULL check file access

Null in ResourceImporterTexture::_save_stex

editor/import/resource_importer_texture.cpp

@@ -308,6 +308,7 @@ void ResourceImporterTexture::save_to_stex_format(FileAccess *f, const Ref<Image
 
 void ResourceImporterTexture::_save_stex(const Ref<Image> &p_image, const String &p_to_path, CompressMode p_compress_mode, float p_lossy_quality, Image::CompressMode p_vram_compression, bool p_mipmaps, bool p_streamable, bool p_detect_3d, bool p_detect_roughness, bool p_detect_normal, bool p_force_normal, bool p_srgb_friendly, bool p_force_po2_for_compressed, uint32_t p_limit_mipmap, const Ref<Image> &p_normal, Image::RoughnessChannel p_roughness_channel) {
 	FileAccess *f = FileAccess::open(p_to_path, FileAccess::WRITE);
+	ERR_FAIL_NULL(f);
 	f->store_8('G');
 	f->store_8('S');
 	f->store_8('T');