Don't crash if trying to send packets from outside graph
Don't crash if trying to send packets from outside graph

sender can be NULL when message comes from outside the graph.
This feature is used in tests.

rraallvv/microflo,microflo/microflo,microflo/microflo,uwekamper/microflo-spiexperiment,microflo/microflo,bergie/microflo,uwekamper/microflo-spiexperiment,bergie/microflo,bergie/microflo,rraallvv/microflo,bergie/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo,uwekamper/microflo-spiexperiment,rraallvv/microflo,uwekamper/microflo-spiexperiment,microflo/microflo