Conform more of the codebase to strictNullChecks (#11100)

src/components/structures/RoomView.tsx

@@ -220,7 +220,6 @@ export interface IRoomState {
     showUrlPreview?: boolean;
     e2eStatus?: E2EStatus;
     rejecting?: boolean;
-    rejectError?: Error;
     hasPinnedWidgets?: boolean;
     mainSplitContentType?: MainSplitContentType;
     // whether or not a spaces context switch brought us here,
@@ -1680,7 +1679,6 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
 
                 this.setState({
                     rejecting: false,
-                    rejectError: error,
                 });
             },
         );
@@ -1714,7 +1712,6 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
 
             this.setState({
                 rejecting: false,
-                rejectError: error,
             });
         }
     };

src/components/structures/ScrollPanel.tsx

@@ -491,7 +491,7 @@ export default class ScrollPanel extends React.Component<IProps> {
         // This would cause jumping to happen on Chrome/macOS.
         return new Promise((resolve) => window.setTimeout(resolve, 1))
             .then(() => {
-                return this.props.onFillRequest(backwards);
+                return this.props.onFillRequest?.(backwards);
             })
             .finally(() => {
                 this.pendingFillRequests[dir] = false;

src/components/structures/TimelinePanel.tsx

@@ -1623,12 +1623,12 @@ class TimelinePanel extends React.Component<IProps, IState> {
             // dialog, let's jump to the end of the timeline. If we weren't,
             // something has gone badly wrong and rather than causing a loop of
             // undismissable dialogs, let's just give up.
-            if (eventId) {
+            if (eventId && this.props.timelineSet.room) {
                 onFinished = () => {
                     // go via the dispatcher so that the URL is updated
                     dis.dispatch<ViewRoomPayload>({
                         action: Action.ViewRoom,
-                        room_id: this.props.timelineSet.room.roomId,
+                        room_id: this.props.timelineSet.room!.roomId,
                         metricsTrigger: undefined, // room doesn't change
                     });
                 };
@@ -2098,7 +2098,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
         // forwards, otherwise if somebody hits the bottom of the loaded
         // events when viewing historical messages, we get stuck in a loop
         // of paginating our way through the entire history of the room.
-        const stickyBottom = !this.timelineWindow.canPaginate(EventTimeline.FORWARDS);
+        const stickyBottom = !this.timelineWindow?.canPaginate(EventTimeline.FORWARDS);
 
         // If the state is PREPARED or CATCHUP, we're still waiting for the js-sdk to sync with
         // the HS and fetch the latest events, so we are effectively forward paginating.

src/components/structures/UserView.tsx

@@ -75,7 +75,7 @@ export default class UserView extends React.Component<IProps, IState> {
         } catch (err) {
             Modal.createDialog(ErrorDialog, {
                 title: _t("Could not load user profile"),
-                description: err && err.message ? err.message : _t("Operation failed"),
+                description: err instanceof Error ? err.message : _t("Operation failed"),
             });
             this.setState({ loading: false });
             return;