I'm a noob at assembly, please be gentle...

I'm having problems running my program on the simulator, I changed the PC directory to 0x00400000 and the program loaded fine, but when I run it I get an error that reads "Memory address out of bounds
Buffer is null in read_string"

#larger.asm

.text
.globl main
main:
##get first number from user store in t0

li $v0, 8
syscall
move $t0, $v0

##Get seconc numer from user, put iton $t1
li $v0, 5
syscall
move $t1, $v0

##put the larger of $t0 and $t1 into $t2
bgt $t0, $t1, t0_bigger
move $t2, $t1
b endif
t0_bigger:
move $t2, $t0
endif:

##Print out $t2
move $a0, $t2
li $v0, 1
syscall

##exit program
li $v0, 10
syscall
##end of larger.asm