Array toolbar should be visually connected to the array children

[sdirix]

Problem [react/material]:

• Array toolbar is not visually connected to its children
• This is the case for the table as well as the layout renderer

Examples:

• Empty space:
  

• Hard to parse visually that Analysis doesn't belong to Sources:
  

[iluuu1994]

First screenshot: I think it could help if "No data" was wrapped in a paper like the elements.

Second screenshot: Spacing between sources and analysis would probably help. Unrelated but I would also move the errors to the left (like in the upper screenshot).