delete associated label if object is removed

web/app/sketcher/parametric.ts

@@ -265,15 +265,18 @@ class ParametricManager {
     obj.constraints.clear();
     obj.generators.clear();
 
-    this.viewer.dimLayer.traverseSketchObjects(dim => {
-      obj.accept(o => {
-        if (dim.dependsOn && dim.dependsOn(o)) {
-          this._removeObject(dim);
-          return false;
-        }
-        return true;
+    [this.viewer.dimLayer, this.viewer.labelLayer].forEach(l => {
+      l.traverseSketchObjects(dim => {
+        obj.accept(o => {
+          if (dim.dependsOn && dim.dependsOn(o)) {
+            this._removeObject(dim);
+            return false;
+          }
+          return true;
+        });
       });
-    });
+    })
+
   };
 
   invalidate() {

web/app/sketcher/shapes/label.ts

@@ -21,6 +21,10 @@ export class Label extends SketchObject {
     this.offsetY = 0;
   }
 
+  dependsOn(other: SketchObject) {
+    return this.assignedObject === other;
+  }
+
   translateImpl(dx, dy) {
     this.offsetX += dx;
     this.offsetY += dy;

web/app/sketcher/shapes/sketch-object.ts

@@ -27,6 +27,10 @@ export abstract class SketchObject extends Shape implements SolvableObject {
     this.id = id || this.ref;
   }
 
+  dependsOn(obj: SketchObject): boolean {
+    return false;
+  };
+
   get isGenerated() {
     let obj: SketchObject = this;
     while (obj) {