When overriding an OnReceivedBroadcast() method, second parameter (string data) is not cleared between calls. I.e. if you get a message, and shorter message after that, there will be remains of the older message at the end of the string - buffer is not cleared.

Reproduction steps:
1. Open the project
2. Open Scenes/Menu
3. Build and launch the build game twice
4. In both running instances:
- Multiplayer - Host
- Enter server name and distinct port. Server names should be of different length, the bigger the difference, the easier to spot the issue
- Hit Start
5. In the editor, hit play
6. Hit multiplayer

Expected: debug messages doesn't overlap
Actual: one debug message overlaps with another one

Reproduced on: 5.5.0f3, 5.5.3f1, 5.6.1p1, 2017.1.0b6