Interactive Highlight highlights something behind dialog when first turned on

[KatieWoe]

Found during phetsims/qa#1335
The first time Interactive Highlights are turned on, an object behind the preferences dialog may be highlighted briefly. Objects were moved around before preferences were opened, and the last object moved seemed to be the one highlighted in this bug.

[pixelzoom]

In Slack#dev-public, @jessegreenberg said:

That is new, thanks for finding. Related to how interactive and focus highlights share the same highlight.

[KatieWoe]

Also seen in phetsims/qa#1339

[pixelzoom]

Thanks @KatieWoe. This will not be addressed for the Vector Addition 1.2 release.