fix crash when post is single line with hashtags

[connyduck]

java.lang.StringIndexOutOfBoundsException
     at android.text.SpannableStringBuilder.<init>(SpannableStringBuilder.java:63)
     at android.text.SpannableStringBuilder.subSequence(SpannableStringBuilder.java:1198)
     at com.keylesspalace.tusky.util.LinkHelper.setClickableText(LinkHelper.kt:99)
     at com.keylesspalace.tusky.adapter.StatusBaseViewHolder.setTextVisible(StatusBaseViewHolder.java:289)
     at com.keylesspalace.tusky.adapter.StatusBaseViewHolder.setSpoilerAndContent(StatusBaseViewHolder.java:244)
     at com.keylesspalace.tusky.adapter.StatusBaseViewHolder.setupWithStatus(StatusBaseViewHolder.java:820)
     at com.keylesspalace.tusky.adapter.StatusViewHolder.setupWithStatus(StatusViewHolder.java:91)
     at com.keylesspalace.tusky.components.timeline.TimelinePagingAdapter.bindViewHolder(TimelinePagingAdapter.kt:100)
     at com.keylesspalace.tusky.components.timeline.TimelinePagingAdapter.onBindViewHolder(TimelinePagingAdapter.kt:82)
     at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7847)
     at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6646)
     at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6917)
     at androidx.recyclerview.widget.GapWorker.prefetchPositionWithDeadline(GapWorker.java:288)
     at androidx.recyclerview.widget.GapWorker.flushTaskWithDeadline(GapWorker.java:345)
     at androidx.recyclerview.widget.GapWorker.flushTasksWithDeadline(GapWorker.java:361)
     at androidx.recyclerview.widget.GapWorker.prefetch(GapWorker.java:368)
     at androidx.recyclerview.widget.GapWorker.run(GapWorker.java:399)
     at android.os.Handler.handleCallback(Handler.java:959)
     at android.os.Handler.dispatchMessage(Handler.java:100)
     at android.os.Looper.loopOnce(Looper.java:232)
     at android.os.Looper.loop(Looper.java:317)
     at android.app.ActivityThread.main(ActivityThread.java:8705)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:886)

[Tak]

🤦