Fix: overwrite buffer in cleanupDatalog()

[dukess]

No description provided.

[dukess]

BTW: should we define separate buffers for client, debug and file outputs?

[fredlcore]

Thanks! I have no Due at the moment where I could check whether this (seriously) affects free RAM, but if the buffers are just created temorarily, then it shouldn't be an issue, right?

[DE-cr]

The use of a temporary char* here doesn't make a difference.
Whether flushToWebClient() does here, I cannot easily tell, but I would expect that right before processing a new url command, that buffer should be flushed.
Anyway, the code change should not hurt, except for a few bytes more in the size of bsb-lan's binary. ;)