crash when opening a .zip file directly from k9mail

==steps to reproduce==

• get an email with a .zip file attached
• open the attachment direcly from K9-mail

==expected result==
Amaze should display the same popup as when I open a locally stored .zip file

==observed behavior==
Amaze crashes.

==versions==

• lineageos-with-microg 15.1 as of 2019-04-10 with addon_root
• Hardware: Mido
• current xposed 90beta3 and xprivacylua from Fdroid, restrict nothing important
• amaze 3.3.2 from fdroid
• K9mail from fdroid

==logs (collected with Scoop)==

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(String.java:1975)
at com.amaze.filemanager.fragments.CompressedExplorerFragment.onActivityCreated(CompressedExplorerFragment.java:208)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2355)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1451)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2245)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:703)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:440)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:108)

Start in CompressedExplorerFragment.java at line 208 and reproduce the crash by opening a ZIP attachment directly from K-9 Mail. Compare that path with opening a locally stored ZIP and verify that the same popup appears without an exception.