strang things about FSM

I found when irq_i is low,then state machine go to 00000h.see picture nether:

another question:does "if...else if.....else "have priority level?

code:

SPI_IDLE_status:

begin

TXBnCTRL_whetherCanTxNext <= 1'b1;

rxdFIFOHaveFrameIrq <= 1'b1;

SPI_other_CANINTF_irq_reg <= 1'b1;

if(!irq_i)

begin

spiStatusMachineReg <=SPI_CANINTF1;

TXBnCTRL_whetherCanTxNext <= 1'b0;

end

else if(transmitFIFOUsedw>>`wholeFrameLength

begin

TXBnCTRL_whetherCanTxNext <= 1'b0;

txd_FIFO_num_reg <= 15;

spiStatusMachineReg <=SPI_SEND_status;

end

else spiStatusMachineReg <=SPI_IDLE_status;

end