message: TransformControlBase fix
diff: @@ -10,7 +10,7 @@ import { PurePluginUIComponent } from '../base';
  import { ParameterControls, ParamOnChange } from '../controls/parameters';
  import { PluginContext } from '../../mol-plugin/context';
  import { ParamDefinition as PD } from '../../mol-util/param-definition';
  -import { Subject } from 'rxjs';
  +import { BehaviorSubject, skip } from 'rxjs';
  import { Icon, RefreshSvg, CheckSvg, ArrowRightSvg, ArrowDropDownSvg, TuneSvg } from '../controls/icons';
  import { ExpandGroup, ToggleButton, Button, IconButton } from '../controls/common';
  @@ -124,7 +124,7 @@ abstract class TransformControlBase<P, S extends TransformControlBase.ComponentS
  abstract getSourceAndTarget(): { a?: StateObject, b?: StateObject, bCell?: StateObjectCell };
  abstract state: S;
  - private busy: Subject<boolean> = new Subject();
  + private busy = new BehaviorSubject(false);
  private onEnter = () => {
  if (this.state.error) return;
  @@ -167,11 +167,11 @@ abstract class TransformControlBase<P, S extends TransformControlBase.ComponentS
  };
  componentDidMount() {
  - this.subscribe(this.plugin.behaviors.state.isBusy, b => {
  - if (this.state.busy !== b) this.busy.next(b);
  + this.subscribe(this.plugin.behaviors.state.isBusy, busy => {
  + if (this.busy.value !== busy) this.busy.next(busy);
  });
  - this.subscribe(this.busy, busy => {
  - if (this.state.busy !== busy) this.setState({ busy });
  + this.subscribe(this.busy.pipe(skip(1)), busy => {
  + this.setState({ busy });
  });
  }
  