Avoid crash when unknown reading mode is used

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -554,11 +554,15 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
     }
 
     private fun showReadingModeToast(mode: Int) {
+        try {
             val strings = resources.getStringArray(R.array.viewers_selector)
             readingModeToast?.cancel()
             readingModeToast = toast(strings[mode]) {
                 it.setGravity(Gravity.CENTER_VERTICAL or Gravity.CENTER_HORIZONTAL, 0, 0)
             }
+        } catch (e: ArrayIndexOutOfBoundsException) {
+            Timber.e("Unknown reading mode: $mode")
+        }
     }
 
     /**