SPI_finish man page
SPI_finish — disconnect a C function from the SPI manager
SPI_finish closes an existing connection to the SPI manager. You must call this function after completing the SPI operations needed during your C function's current invocation. You do not need to worry about making this happen, however, if you abort the transaction via elog(ERROR). In that case SPI will clean itself up automatically.
if properly disconnected
if called from an unconnected C function