add NullDrawerState class

src/main/java/shape/tp5/NullDrawerState.java

+package shape.tp5;
+
+import javafx.scene.canvas.GraphicsContext;
+
+
+public class NullDrawerState implements DrawerState {
+
+
+    @Override
+    public void mousePressed(DrawerContext context, double x, double y) {
+
+    }
+
+    @Override
+    public void mouseReleased(DrawerContext context, double x, double y) {
+
+    }
+
+    @Override
+    public void mouseMoved(DrawerContext context, double x, double y) {
+
+    }
+
+    @Override
+    public void paint(DrawerContext context, GraphicsContext graphicsContext) {
+
+    }
+}