Error when placing any amount of robots in the simulator

[grandec]

If just one robot is placed, this error is given at the rosbridge_server terminal:

[ERROR] [1504056832.879547]: [Client 22] publish: <class 'struct.error'>: 'pack expected 6 items for packing (got 7)' when writing 'x: [0, 196, 0, 0, 0, 0, 0]
y: [0, 196, 0, 0, 0, 0, 0]
th: [0, 7853985, 0, 0, 0, 0, 0]
ball_x: 0
ball_y: 0'

if two the packing gets with 8 itens, and so on.
So the message is not being correctly created.