Could be, easy to verify
Code:
    ' Wait for data from GPS
    serin2 GPS_RX,85,[gps_char] 'If I remove this line or disconnect the GPS, MCU will crash!
    ' Store data in buffer
    gps_data[i] = gps_char
    i = i + 1

   If i >= 80  'or whatever size you set the array to
     serout2 portc.5,84, ["Next char will overrun buffer"]
   ENDIF