Avoid updating pdo if buffer not set

[nicolas71640]

If no buffer has been set as input or output pdo, don't update them, avoiding null pointer exception

[github-actions]

File	Coverage	Lines	Branches
All files	49%	51%	46%	❌
lib/include/kickcat/Error.h	87%	92%	83%	✅
lib/include/kickcat/Ring.h	0%	0%	0%	❌
lib/include/kickcat/SBufQueue.h	0%	0%	0%	❌
lib/include/kickcat/Units.h	0%	0%	100%	❌
lib/include/kickcat/protocol.h	61%	73%	50%	❌
lib/include/kickcat/CoE/EsiParser.h	0%	0%	0%	❌
lib/include/kickcat/CoE/OD.h	50%	50%	0%	❌
lib/include/kickcat/CoE/mailbox/request.h	83%	66%	100%	✅
lib/include/kickcat/CoE/mailbox/response.h	66%	33%	100%	❌
lib/master/include/kickcat/Bus.h	71%	100%	42%	❌
lib/master/include/kickcat/Link.h	92%	85%	100%	✅
lib/master/src/Bus.cc	83%	85%	81%	✅
lib/master/src/CoE.cc	88%	95%	82%	✅
lib/master/src/Link.cc	98%	100%	97%	✅
lib/master/src/Prints.cc	51%	38%	64%	❌
lib/master/src/Slave.cc	50%	50%	0%	❌
lib/slave/include/kickcat/AbstractESC.h	83%	66%	100%	✅
lib/slave/include/kickcat/ESM.h	91%	83%	100%	✅
lib/slave/include/kickcat/ESC/EmulatedESC.h	0%	0%	100%	❌
lib/slave/src/AbstractESC.cc	87%	97%	78%	✅
lib/slave/src/AbstractEmulatedEEPROM.cc	0%	0%	0%	❌
lib/slave/src/AbstractSPI.cc	0%	0%	100%	❌
lib/slave/src/ESMStates.cc	92%	98%	86%	✅
lib/slave/src/ESM.cc	89%	89%	90%	✅
lib/slave/src/PDO.cc	86%	92%	80%	✅
lib/slave/src/EEPROM/EEPROM_factory.cc	0%	0%	100%	❌
lib/slave/src/ESC/EmulatedESC.cc	0%	0%	0%	❌
lib/slave/src/slave/Slave.cc	0%	0%	0%	❌
lib/src/Error.cc	0%	0%	0%	❌
lib/src/Frame.cc	87%	92%	82%	✅
lib/src/Mailbox.cc	51%	57%	45%	❌
lib/src/SIIParser.cc	93%	95%	91%	✅
lib/src/TapSocket.cc	0%	0%	0%	❌
lib/src/protocol.cc	77%	75%	80%	✅
lib/src/CoE/EsiParser.cc	0%	0%	0%	❌
lib/src/CoE/OD.cc	11%	17%	4%	❌
lib/src/CoE/protocol.cc	34%	39%	29%	❌
lib/src/CoE/mailbox/request.cc	54%	57%	52%	❌
lib/src/CoE/mailbox/response.cc	26%	27%	24%	❌
simulation/network_simulator.cc	0%	0%	0%	❌

Minimum allowed coverage is 75%

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