Ensure message details video container matches placement of recycler.

app/src/main/res/layout/message_details_activity.xml

@@ -30,8 +30,12 @@
 
     <FrameLayout
         android:id="@+id/video_container"
-        android:layout_width="match_parent"
-        android:layout_height="match_parent" />
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/toolbar"  />
 
     <androidx.recyclerview.widget.RecyclerView
         android:id="@+id/message_details_list"