Roots on SD cards can't be opened

Device: Huawei MatePad, Android 10
Any root on SD card fails to be opened:
```
07-22 10:50:36.740 16387 17755 D previews: previews provided in 145275ms
07-22 10:50:36.783 16387 17755 D resources-index: 3179 resources returned
07-22 10:50:36.814 16387 17755 D tags-storage: file /storage/9C33-6BBD/Android/media/com.github.catfriend1.syncthingandroid/Camera/.ark/tags exists, last modified at 2022-07-21T19:28:50Z
07-22 10:50:36.833 16387 17755 D tags-storage: 501 entries has been read
07-22 10:50:36.835 16387 17755 D tags-storage: forgetting 0 resources
07-22 10:50:36.940 16387 16399 E : [ZeroHung]zrhung_get_config: Get config failed for wp[0x0008]
--------- beginning of crash
07-22 10:50:36.972 16387 16387 E AndroidRuntime: FATAL EXCEPTION: main
07-22 10:50:36.972 16387 16387 E AndroidRuntime: Process: space.taran.arknavigator, PID: 16387
07-22 10:50:36.972 16387 16387 E AndroidRuntime: java.nio.file.AccessDeniedException: /storage/9C33-6BBD/Android/media/com.github.catfriend1.syncthingandroid/Camera/.ark/tags
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at sun.nio.fs.UnixFileSystemProvider.newByteChannel(UnixFileSystemProvider.java:214)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:434)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at java.nio.file.Files.newOutputStream(Files.java:216)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at java.nio.file.Files.write(Files.java:3351)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$writeStorage$2.invokeSuspend(PlainTagsStorage.kt:227)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$writeStorage$2.invoke(Unknown Source:8)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$writeStorage$2.invoke(Unknown Source:4)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:89)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:165)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt.withContext(Unknown Source:1)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage.writeStorage(PlainTagsStorage.kt:216)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage.access$writeStorage(PlainTagsStorage.kt:26)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$persist$2.invokeSuspend(PlainTagsStorage.kt:183)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$persist$2.invoke(Unknown Source:8)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$persist$2.invoke(Unknown Source:4)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:89)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:165)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt.withContext(Unknown Source:1)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage.persist(PlainTagsStorage.kt:131)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage.access$persist(PlainTagsStorage.kt:26)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$cleanup$2.invokeSuspend(PlainTagsStorage.kt:121)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$cleanup$2.invoke(Unknown Source:8)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage$cleanup$2.invoke(Unknown Source:4)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:89)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:165)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.BuildersKt.withContext(Unknown Source:1)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.PlainTagsStorage.cleanup(PlainTagsStorage.kt:116)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at space.taran.arknavigator.mvp.model.repo.tags.TagsStorageRepo$provide$2.invokeSuspend(TagsStorageRepo.kt:37)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:750)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678)
07-22 10:50:36.972 16387 16387 E AndroidRuntime: at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665)
```

Start with PlainTagsStorage.kt around persist, cleanup, and writeStorage at lines 116, 131, 183, 216, and 227, where the stack trace shows the SD-card tags file write failing. Reproduce by opening a root on an SD card in the Android app and verify that the root opens without the AccessDeniedException crash.

Written by the indexing model from the issue text.