slimlock sudo make panel error?

[themagictool]

After I typed sudo make it gave me an error that says:

panel.cpp: In constructor 'Panel: :Panel(Display*, int, Window, Cfg*, const stringent &)':
panel.cpp:47:15: error: ordered comparison of pointer with integer zero ('GC' {aka '_XGC*'} and 'int')
47 | if (WinGC < 0) {
| ~~~~~~^~~
make : *** [Makefile:29: panel.o] Error 1

I just started using Linux a few days ago and I'm a complete beginner. How do I fix this?

[VaughnValle]

Which command is producing this error?