Fix crash when deleting room summary

Since this is used across different threads, we have to delete it on the
event loop.

Thank you, q234rty, for the help with debugging this.

src/timeline/InputBar.h

@@ -25,6 +25,15 @@ class CombinedImagePackModel;
 class QMimeData;
 class QDropEvent;
 
+struct DeleteLaterDeleter
+{
+    void operator()(QObject *p)
+    {
+        if (p)
+            p->deleteLater();
+    }
+};
+
 enum class MarkdownOverride
 {
     NOT_SPECIFIED, // no override set
@@ -278,14 +287,6 @@ private:
     bool uploading_      = false;
     bool containsAtRoom_ = false;
 
-    struct DeleteLaterDeleter
-    {
-        void operator()(QObject *p)
-        {
-            if (p)
-                p->deleteLater();
-        }
-    };
     using UploadHandle = std::unique_ptr<MediaUpload, DeleteLaterDeleter>;
     std::vector<UploadHandle> unconfirmedUploads;
     std::vector<UploadHandle> runningUploads;

src/timeline/TimelineModel.h

@@ -493,8 +493,8 @@ private:
     std::string last_event_id;
     std::string fullyReadEventId_;
 
-    std::unique_ptr<RoomSummary> parentSummary = nullptr;
+    std::unique_ptr<RoomSummary, DeleteLaterDeleter> parentSummary = nullptr;
-    bool parentChecked                         = false;
+    bool parentChecked                                             = false;
 };
 
 template<class T>