removed warning

lib/lbm.c

@@ -46,7 +46,10 @@ int main()
         }
 
         show_pixels(context, nx, ny);
-        int mask_id = gfx_left_right_mouse_pressed(&p);
+        int id = gfx_left_right_mouse_pressed(&p);
+        if (id) {
+            printf("A valid mouse clic was performed.\n");
+        }
 
         it += 1;
     }