TM4C123GH6PM: Trying to get ADC working, please help.

I am trying to sample PE3 for a Sonar sensor, but my code never enters the ISR. I have updated my vector table with the "ADC_read_fxn" handler, but constantly just end up with "No source available for "0xfffffffe"  errors. Any help would be greatly appreciated. 

#include "sonar_init.h"

float distInch;
volatile unsigned int proflag=0;

void sonarInit(void)
{

    //SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralReset(SYSCTL_PERIPH_ADC0);
    ADCSequenceDisable(ADC0_BASE,3);

    ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);

    ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 | ADC_CTL_IE | ADC_CTL_END);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
    ADCIntRegister(ADC0_BASE,3, &ADC_read_fxn);
    ADCIntEnable(ADC0_BASE,3);\
    ADCIntClear(ADC0_BASE, 3);
    ADCSequenceEnable(ADC0_BASE,3);

    IntMasterEnable();

}

void main(void)
{
    sonarInit();

    while(1){
        if (proflag==0){
       ADCProcessorTrigger(ADC0_BASE,3);
       proflag=1;
        }
    }
}


void ADC_read_fxn(void)
{
  ADCIntClear(ADC0_BASE,3);
  while(!ADCIntStatus(ADC0_BASE, 3, false));
  uint32_t rawADC;
  ADCSequenceDataGet(ADC0_BASE, 3, &rawADC);
  distInch=rawADC*102.4;
  proflag=0;
}