fix grbl lib compile

lib/GRBL/include/GRBL.h

@@ -7,7 +7,7 @@
 class iGRBL{
 public:
     virtual void init(int speed, double pas, int accel, String mode = "distance") = 0;
-    virtual void mouveForward(int mm = 5) = 0;
+    virtual void mouveForward(int mm) = 0;
 };
 
 class GRBL : public iGRBL{

lib/GRBL/src/GRBL.cpp

@@ -27,7 +27,7 @@ void GRBL::init(int speed, double pas, int accel, String mode){
     Serial.println(s);
 }
 
-void GRBL::mouveForward(int mm = 5){
+void GRBL::mouveForward(int mm){
     char s[1024];
     sprintf(s, "G1 X%d", mm);
     this->grbl->sendGcode(s);

src/main.cpp

@@ -90,7 +90,7 @@ void loop() {
     }
 
     if (M5.BtnB.wasPressed()) {
-        grbl->mouveForward(50);
+        grbl->mouveForward(-50);
     }
 
     if (M5.BtnC.wasReleased()) {