examples/embedding: Fix reference to freed memory, lexer src name.
examples/embedding: Fix reference to freed memory, lexer src name.

This issue was brought up by BramPeters in the forum:
https://forum.micropython.org/viewtopic.php?p=30066

adafruit/circuitpython,selste/micropython,trezor/micropython,bvernoux/micropython,selste/micropython,pramasoul/micropython,tobbad/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,tobbad/micropython,MrSurly/micropython,kerneltask/micropython,kerneltask/micropython,henriknelson/micropython,pfalcon/micropython,trezor/micropython,pozetroninc/micropython,pfalcon/micropython,pramasoul/micropython,adafruit/circuitpython,adafruit/circuitpython,kerneltask/micropython,pozetroninc/micropython,pramasoul/micropython,MrSurly/micropython,MrSurly/micropython,pfalcon/micropython,henriknelson/micropython,henriknelson/micropython,trezor/micropython,MrSurly/micropython,pozetroninc/micropython,pramasoul/micropython,kerneltask/micropython,pozetroninc/micropython,pfalcon/micropython,adafruit/circuitpython,tobbad/micropython,tobbad/micropython,pozetroninc/micropython,bvernoux/micropython,henriknelson/micropython,bvernoux/micropython,tobbad/micropython,MrSurly/micropython,trezor/micropython,pfalcon/micropython,selste/micropython,pramasoul/micropython,selste/micropython,trezor/micropython,selste/micropython,bvernoux/micropython,adafruit/circuitpython,kerneltask/micropython