check for non-null flyout

src/containers/blocks.jsx

@@ -259,7 +259,7 @@ class Blocks extends React.Component {
     }
 
     onTargetsUpdate () {
-        if (this.props.vm.editingTarget) {
+        if (this.props.vm.editingTarget && this.workspace.getFlyout()) {
             ['glide', 'move', 'set'].forEach(prefix => {
                 this.updateToolboxBlockValue(`${prefix}x`, Math.round(this.props.vm.editingTarget.x).toString());
                 this.updateToolboxBlockValue(`${prefix}y`, Math.round(this.props.vm.editingTarget.y).toString());