Ensure errors when creating a DM are raised to the user

Fixes https://github.com/vector-im/riot-web/issues/12186

Note: this will still result in an empty room being created, but that's a Synapse issue and not something we can solve.

src/components/views/dialogs/AskInviteAnywayDialog.js

@@ -72,7 +72,7 @@ export default createReactClass({
                     <button onClick={this._onInviteNeverWarnClicked}>
                         { _t('Invite anyway and never warn me again') }
                     </button>
-                    <button onClick={this._onInviteClicked} autoFocus="true">
+                    <button onClick={this._onInviteClicked} autoFocus={true}>
                         { _t('Invite anyway') }
                     </button>
                 </div>