fix crash in ReaderActivity (#6439)

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

@@ -159,8 +159,8 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
         applyAppTheme(preferences)
 
         // Setup shared element transitions
+        window.requestFeature(Window.FEATURE_ACTIVITY_TRANSITIONS)
         findViewById<View>(android.R.id.content)?.let { contentView ->
-            window.requestFeature(Window.FEATURE_ACTIVITY_TRANSITIONS)
             contentView.transitionName = SHARED_ELEMENT_NAME
             setEnterSharedElementCallback(MaterialContainerTransformSharedElementCallback())
             window.sharedElementEnterTransition = buildContainerTransform(true)