Conform more of the codebase to strictNullChecks (#10602)

* Conform more of the codebase to `strictNullChecks`

* Conform more of the codebase to `strictNullChecks`

* Fix types

src/components/views/dialogs/CreateSubspaceDialog.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { RefObject, useRef, useState } from "react";
+import React, { useRef, useState } from "react";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { JoinRule } from "matrix-js-sdk/src/@types/partials";
 import { logger } from "matrix-js-sdk/src/logger";
@@ -41,9 +41,9 @@ const CreateSubspaceDialog: React.FC<IProps> = ({ space, onAddExistingSpaceClick
 
     const [busy, setBusy] = useState<boolean>(false);
     const [name, setName] = useState("");
-    const spaceNameField = useRef() as RefObject<Field>;
+    const spaceNameField = useRef<Field>(null);
     const [alias, setAlias] = useState("");
-    const spaceAliasField = useRef() as RefObject<RoomAliasField>;
+    const spaceAliasField = useRef<RoomAliasField>(null);
     const [avatar, setAvatar] = useState<File | undefined>();
     const [topic, setTopic] = useState<string>("");
 

src/components/views/dialogs/ExportDialog.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { useRef, useState, Dispatch, SetStateAction, RefObject } from "react";
+import React, { useRef, useState, Dispatch, SetStateAction } from "react";
 import { Room } from "matrix-js-sdk/src/matrix";
 import { logger } from "matrix-js-sdk/src/logger";
 
@@ -104,8 +104,8 @@ const ExportDialog: React.FC<IProps> = ({ room, onFinished }) => {
     } = useExportFormState();
 
     const [isExporting, setExporting] = useState(false);
-    const sizeLimitRef = useRef() as RefObject<Field>;
-    const messageCountRef = useRef() as RefObject<Field>;
+    const sizeLimitRef = useRef<Field>(null);
+    const messageCountRef = useRef<Field>(null);
     const [exportProgressText, setExportProgressText] = useState(_t("Processing…"));
     const [displayCancel, setCancelWarning] = useState(false);
     const [exportCancelled, setExportCancelled] = useState(false);

src/components/views/dialogs/RegistrationEmailPromptDialog.tsx

@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import * as React from "react";
-import { RefObject, SyntheticEvent, useRef, useState } from "react";
+import { SyntheticEvent, useRef, useState } from "react";
 
 import { _t, _td } from "../../../languageHandler";
 import Field from "../elements/Field";
@@ -30,7 +30,7 @@ interface IProps {
 
 const RegistrationEmailPromptDialog: React.FC<IProps> = ({ onFinished }) => {
     const [email, setEmail] = useState("");
-    const fieldRef = useRef() as RefObject<Field>;
+    const fieldRef = useRef<Field>(null);
 
     const onSubmit = async (e: SyntheticEvent): Promise<void> => {
         e.preventDefault();

src/components/views/dialogs/ReportEventDialog.tsx

@@ -255,7 +255,7 @@ export default class ReportEventDialog extends React.Component<IProps, IState> {
                 });
             } else {
                 // Report to homeserver admin through the dedicated Matrix API.
-                await client.reportEvent(ev.getRoomId(), ev.getId(), -100, this.state.reason.trim());
+                await client.reportEvent(ev.getRoomId()!, ev.getId()!, -100, this.state.reason.trim());
             }
 
             // if the user should also be ignored, do that
@@ -340,7 +340,7 @@ export default class ReportEventDialog extends React.Component<IProps, IState> {
                     );
                     break;
                 case NonStandardValue.Admin:
-                    if (client.isRoomEncrypted(this.props.mxEvent.getRoomId())) {
+                    if (client.isRoomEncrypted(this.props.mxEvent.getRoomId()!)) {
                         subtitle = _t(
                             "This room is dedicated to illegal or toxic content " +
                                 "or the moderators fail to moderate illegal or toxic content.\n" +

src/components/views/dialogs/spotlight/SpotlightDialog.tsx

@@ -288,8 +288,8 @@ interface IDirectoryOpts {
 }
 
 const SpotlightDialog: React.FC<IProps> = ({ initialText = "", initialFilter = null, onFinished }) => {
-    const inputRef = useRef() as RefObject<HTMLInputElement>;
-    const scrollContainerRef = useRef() as RefObject<HTMLDivElement>;
+    const inputRef = useRef<HTMLInputElement>(null);
+    const scrollContainerRef = useRef<HTMLDivElement>(null);
     const cli = MatrixClientPeg.get();
     const rovingContext = useContext(RovingTabIndexContext);
     const [query, _setQuery] = useState(initialText);