Fix BUTTON_EXISTS and misplaced comma (#13411)

Fixes #13410 and redeclaration of `BUTTON_EXISTS`

Marlin/src/lcd/ultralcd.h

 
 #else
 
+  #undef BUTTON_EXISTS
   #define BUTTON_EXISTS(BN) false
 
   // Shift register bits correspond to buttons:

Marlin/src/module/temperature.cpp

           MSG_PID_DEBUG_PTERM, work_pid[HOTEND_INDEX].Kp,
           MSG_PID_DEBUG_ITERM, work_pid[HOTEND_INDEX].Ki,
           MSG_PID_DEBUG_DTERM, work_pid[HOTEND_INDEX].Kd
-          #if ENABLED(PID_EXTRUSION_SCALING),
-            MSG_PID_DEBUG_CTERM, work_pid[HOTEND_INDEX].Kc
+          #if ENABLED(PID_EXTRUSION_SCALING)
+            , MSG_PID_DEBUG_CTERM, work_pid[HOTEND_INDEX].Kc
           #endif
         );
       #endif