fix to show link target when selected

[HiroyasuNishiyama]

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

If the target of the Link node exists in another tab, selecting the virtual node will move to the tab of target node, but not the target node is not shown.
This fix show the target node after moving tab if there is only one target node in target tab.

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage remained the same at 67.37% when pulling 7e7f481 on node-red-hitachi:fix-link-target-select into 3e0f080 on node-red:master.