don't display acc data when AB added (#1483)

* don't display acc data when AB added

* hide acc

sim/visuals/microbit.ts

@@ -720,6 +720,12 @@ path.sim-board {
             el.style.perspectiveOrigin = "50% 50% 50%";
             el.style.perspective = "30em";
 
+            // don't display acc data when AB is on
+            if (state.buttonPairState.usesButtonAB) {
+                if (this.accTextX) this.accTextX.textContent = "";
+                if (this.accTextY) this.accTextY.textContent = "";
+                if (this.accTextZ) this.accTextZ.textContent = "";
+            } else {
                 // update text
                 if (acc.flags & AccelerometerFlag.X) {
                     if (!this.accTextX) {
@@ -743,6 +749,7 @@ path.sim-board {
                     this.accTextZ.textContent = `az:${z}`;
                 }
             }
+        }
 
         private buildDom() {
             this.element = <SVGSVGElement>svg.elt("svg")