Conform more of the code base to strict null checking (#10147)

* Conform more of the code base to strict null checking

* More strict fixes

* More strict work

* Fix missing optional type

* Iterate

src/components/views/audio_messages/Clock.tsx

@@ -43,7 +43,7 @@ export default class Clock extends React.Component<Props> {
         return currentFloor !== nextFloor;
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return (
             <span aria-live={this.props["aria-live"]} role={this.props.role} className="mx_Clock">
                 {this.props.formatFn(this.props.seconds)}

src/components/views/audio_messages/DurationClock.tsx

@@ -48,7 +48,7 @@ export default class DurationClock extends React.PureComponent<IProps, IState> {
         this.setState({ durationSeconds: time[1] });
     };
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return <Clock seconds={this.state.durationSeconds} />;
     }
 }

src/components/views/audio_messages/LiveRecordingClock.tsx

@@ -59,7 +59,7 @@ export default class LiveRecordingClock extends React.PureComponent<IProps, ISta
         });
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return <Clock seconds={this.state.seconds} aria-live="off" />;
     }
 }

src/components/views/audio_messages/LiveRecordingWaveform.tsx

@@ -63,7 +63,7 @@ export default class LiveRecordingWaveform extends React.PureComponent<IProps, I
         this.setState({ waveform: this.waveform });
     }
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return <Waveform relHeights={this.state.waveform} />;
     }
 }

src/components/views/audio_messages/PlaybackClock.tsx

@@ -65,7 +65,7 @@ export default class PlaybackClock extends React.PureComponent<IProps, IState> {
         this.setState({ seconds: time[0], durationSeconds: time[1] });
     };
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         let seconds = this.state.seconds;
         if (this.state.playbackPhase === PlaybackState.Stopped) {
             if (Number.isFinite(this.props.defaultDisplaySeconds)) {

src/components/views/audio_messages/PlaybackWaveform.tsx

@@ -61,7 +61,7 @@ export default class PlaybackWaveform extends React.PureComponent<IProps, IState
         this.setState({ progress });
     };
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return <Waveform relHeights={this.state.heights} progress={this.state.progress} />;
     }
 }

src/components/views/audio_messages/Waveform.tsx

@@ -41,7 +41,7 @@ export default class Waveform extends React.PureComponent<IProps, IState> {
         progress: 1,
     };
 
-    public render(): JSX.Element {
+    public render(): React.ReactNode {
         return (
             <div className="mx_Waveform">
                 {this.props.relHeights.map((h, i) => {