Mic bargraph silent

[f1rmb]

Hi,
This get rid of one GCC warning, and keep the mic bargraph hidden when app menu is displayed.

Cheers.

Daniel

[travisgoodspeed]

I'll be happy to merge this once all tests are passing, but a function prototype seems to be missing.

src/display.c: In function 'draw_micbargraph':
src/display.c:95:5: error: implicit declaration of function 'Menu_IsVisible' [-Werror=implicit-function-declaration]
     if( gui_opmode2 == OPM2_MENU || Menu_IsVisible() ) {
     ^
cc1: all warnings being treated as errors
make[3]: *** [display.o] Error 1

[f1rmb]

Oops, I guessed app menu was always used ;-).
Fix on the go.

Cheers.