Add information for Timeline plugin when no time dimension layer is selected in TOC

[subashtiwari1010]

Description

When the layer with time dimension is disabled in TOC, then clicking the timeline button does not do anything.

How to reproduce

• Add a layer with time dimension
• Add a widget for the layer
• Uncheck the layer in TOC
• Click the timeline button in footer
• Nothing is visible

Expected Result
If there is no layers then it should provide some information saying no time dimension layer is selected or the tool should be disabled.

Current Result
Nothing is visible (neither the timeline nor the information)

• Not browser related

Browser info

(use this site: https://www.whatsmybrowser.org/ for non expert users)

Browser Affected	Version
Internet Explorer
Edge
Chrome
Firefox
Safari

Other useful information

[tdipisa]

@subashtiwari1010 when the no temporal layers are active in TOC, usually the Timeline plugin disappear. This is the reason why if you click on the button below (which is appearing only if there are widgets on map) nothing happens.

You are right anyway, better user feedback should be provided or, maybe better, that button should removed completely until a temporal layer is selected again in TOC.