java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.io.File.getPath()' on a null object reference

This is the consol message when I tried to download task
```

Backoff delay duration less than minimum value
I/flutter (22485): f774957b-612b-4aac-857a-8c817e3f8e33
D/EGL_emulation(22485): eglCreateContext: 0xf4066ff0: maj 2 min 0 rcv 2
D/EGL_emulation(22485): eglCreateContext: 0xf4066960: maj 2 min 0 rcv 2
D/HostConnection(22485): HostConnection::get() New Host Connection established 0xf4068090, tid 22562
D/HostConnection(22485): HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_has_shared_slots_host_memory_allocator ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data ANDROID_EMU_read_color_buffer_dma GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_gles_max_version_2
D/EGL_emulation(22485): eglMakeCurrent: 0xf4066960: ver 2 0 (tinfo 0xb32a4450) (first time)
D/PathProviderPlugin(22485): Use TaskQueues.
D/DownloadWorker(22485): DownloadWorker{url=[https://cdn.syncfusion.com/content/PDFViewer/flutter-succinctly.pdf,filename=null,savedDir=/storage/emulated/0/Download,header=,isResume=false,status=1]()
D/DownloadWorker(22485): Update notification: {notificationId: 5, title: [https://cdn.syncfusion.com/content/PDFViewer/flutter-succinctly.pdf](), status: 2, progress: 0}
D/DownloadWorker(22485): Open connection to [https://cdn.syncfusion.com/content/PDFViewer/flutter-succinctly.pdf]()
D/DownloadWorker(22485): Content-Type = application/pdf
D/DownloadWorker(22485): Content-Length = 4186004
D/DownloadWorker(22485): Charset = null
D/DownloadWorker(22485): Content-Disposition = null
D/DownloadWorker(22485): fileName = flutter-succinctly.pdf
E/DownloadWorker(22485): It looks like you are trying to save file in public storage but not setting 'saveInPublicStorage' to 'true'
D/DownloadWorker(22485): Update notification: {notificationId: 5, title: [https://cdn.syncfusion.com/content/PDFViewer/flutter-succinctly.pdf](), status: 4, progress: -1}
W/System.err(22485): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.io.File.getPath()' on a null object reference
W/System.err(22485): at vn.hunghd.flutterdownloader.DownloadWorker.downloadFile(DownloadWorker.java:398)
W/System.err(22485): at vn.hunghd.flutterdownloader.DownloadWorker.doWork(DownloadWorker.java:235)
W/System.err(22485): at androidx.work.Worker$1.run(Worker.java:86)
W/System.err(22485): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
W/System.err(22485): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
W/System.err(22485): at java.lang.Thread.run(Thread.java:923)
I/WM-WorkerWrapper(22485): Worker result FAILURE for Work [ id=f774957b-612b-4aac-857a-8c817e3f8e33, tags={ flutter_download_task, vn.hunghd.flutterdownloader.DownloadWorker } ]
I/flutter (22485): Fatal: could not find callback
D/HostConnection(22485): HostConnection::get() New Host Connection established 0xf406b4a0, tid 22560
F/libc (22485): FORTIFY: pthread_mutex_lock called on a destroyed mutex (0xc4931d28)
F/libc (22485): Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 22516 (1.ui), pid 22485 (ample.task_flow)
Lost connection to device.

```