Bug Description:

When certain sidebar elements have focus, clicking on the menu bar does not open the selected menu group, but appears to 'weaken' the focus on the element, thus another click will open the menu group.

Clicking again on the menu group to close it returns focus to the original element and so the bug will repeat if attempting to reopen the menu.

For an example of 'weakening focus': when the search input box has focus, the first click on the menu bar will remove the "(up/down for history)" text from the input box, but the insertion caret will still be flashing.

Steps to Reproduce:

1. Click inside an affected sidebar panel or on it's icon in the side panel selector
2. Click on the menu bar

Here is the results of my experimentation on whether different sidebar elements exhibit the bug behaviour (Yes means affected):
Explorer

• Explorer heading: No
• Open Editors sub-heading: No
• Open Editors box: No
• Project Folder sub-heading: No
• Project Folder box: Yes
  Search
• Search heading: No
• Search input box: Yes (and each toggle box - Match case, etc)
• Toggle replace button: Yes
• Replace input box: Yes
• Search results box: Yes
  Source Control
• Source Control heading: No
• Rest of box: Yes
• (Note that due to Extension pages do not load and extensions do not install #14001 I cannot install any SCM extensions, thus I cannot try any other elements)
  Debug
• No elements appear to be affected
  Extensions
• Extensions heading: No
• Search input box: Yes
• Recommended sub-heading: No
• Recommended box: Yes
• Installed sub-heading: No
• Installed box: Yes
  Testing
• Testing heading: No
• Test explorer sub-heading: No
• Test explorer box: Yes
• Test runs sub-heading: No
• Test runs box : No

Additional Information

• Operating System: Windows 10 (Build 19045.4651)
• Theia Version: 1.51.0