PushImpl.ts Socket#onerror attempting to use undefined variable

While running some OpenLiberty FAT tests, specifically io.openliberty.org.apache.myfaces.4.0_fat/WebSocketTests, we discovered a small bug where JSON.parse(event.data) was running where event.data was undefined.
Here is the line it occurs: https://github.com/apache/myfaces/blob/dae36dde5cc42208d034dda23107ad79f68ecc3a/api/src/client/typescript/faces/impl/PushImpl.ts#L156
Volodymyr created a GitHub issue describing the issue here: Faces 4.0 Fix WebSocketTests so that "onerror listener" occurs - Issue #27598 - OpenLiberty/open-liberty (github.com)

Proposed Solution: Change

 JSON.parse(event.data) 

to

JSON.parse(event.data === undefined ? null : event.data)