When execution fails it's the only way to change the prompt showing the
last executed instruction. Example:
```
NEO-GO-VM > loadgo examples/engine/engine.go
READY: loaded 117 instructions
NEO-GO-VM 0 > run
Error: at instruction 3 (SYSCALL): failed to invoke syscall 805851437: syscall not found
NEO-GO-VM 8 > parse
Error: missing argument
NEO-GO-VM 8 > parse 123
Integer to Hex 7b
Integer to Base64 ew==
String to Hex 313233
String to Base64 MTIz
NEO-GO-VM 8 > unload
NEO-GO-VM > exit
```
e8ec820d2e