No preview available: swiping back to an image, and then attempting to download full res crash: IllegalStateException: Fragment PreviewImageFragment

[jtagcat]

Steps to reproduce

1. Open an image without previee
2. You get a banner of 'No resized image available. Download full image?`
3. Swipe left/right to a different image
4. Swipe back to an image
5. Press 'Yes on the prompt'
6. Crash

Actual behaviour

************ CAUSE OF ERROR ************

java.lang.IllegalStateException: Fragment PreviewImageFragment{664772} (9721b654-8491-43f8-a319-f75dd1f46fa2)} not attached to a context.
	at androidx.fragment.app.Fragment.requireContext(Fragment.java:805)
	at androidx.fragment.app.Fragment.getResources(Fragment.java:869)
	at com.owncloud.android.ui.preview.PreviewImageFragment.lambda$setErrorPreviewMessage$2$PreviewImageFragment(PreviewImageFragment.java:744)
	at com.owncloud.android.ui.preview.-$$Lambda$PreviewImageFragment$lYlNRKiEmwgldJH0g5sQ-_uYXY4.onClick(Unknown Source:2)
	at com.google.android.material.snackbar.Snackbar$1.onClick(Snackbar.java:307)
	at android.view.View.performClick(View.java:7259)
	at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992)
	at android.view.View.performClickInternal(View.java:7236)
	at android.view.View.access$3600(View.java:801)
	at android.view.View$PerformClick.run(View.java:27892)
	at android.os.Handler.handleCallback(Handler.java:883)
	at android.os.Handler.dispatchMessage(Handler.java:100)
	at android.os.Looper.loop(Looper.java:214)
	at android.app.ActivityThread.main(ActivityThread.java:7356)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:491)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:940)

************ APP INFORMATION ************
ID: com.nextcloud.client
Version: 30140190
Build flavor: generic

************ DEVICE INFORMATION ************
Brand: OnePlus
Device: OnePlus5T
Model: ONEPLUS A5010
Id: QQ3A.200805.001
Product: OnePlus5T

************ FIRMWARE ************
SDK: 29
Release: 10
Incremental: 9cce4d08bf

Can you reproduce this problem on https://try.nextcloud.com?

Yes

Environment data

Dumpling Lineage latest (no google apps and services and stuff, though it's the fdroid version).

NOTE: Be super sure to remove sensitive data like passwords, note that everybody can look here! You can use the Issue Template application to prefill some of the required information: https://apps.nextcloud.com/apps/issuetemplate

[tobiasKaminsky]

Related to #8054

[parneet-guraya]

The snackbar message keeps showing even if we're away from the image on which it was shown. Now fragment is detached but snackbar still carry the lambda and now pressing download would cause a crash.

I fixed here the snackbar to be shown only in the respective fragment in which the error occurred. So now it won't happen. Here: #13512