I noticed what looks like a copy/paste error in UART_Adapter.c. In the LPUART_Initialize, UART_Initialize, and LPSCI_Initialize functions, the initialization of the state doesn't assign NULL to pTxData (but instead assigns pRxData twice). For example...
base = mLpuartBase[instance];
pLpuartStates[instance] = pState;
pState->rxCbParam = 0;
pState->txCbParam = 0;
pState->pRxData = NULL;
pState->pRxData = NULL;
pState->rxSize = 0;
pState->txSize = 0;
I believe the line in red should read:
pState->pTxData = NULL;
Ryan