Title of book reference doesn't show in ref formatting.

[paulgirard]

Describe the bug
Title of book reference doesn't show in ref formatting.

To Reproduce
Steps to reproduce the behavior:

1. add this reference to the library :

@book{findlay_power_2009,
	isbn={978-0-691-14327-9},
	language={English},
	publisher={Princeton University Press},
	address={Princeton, N.J.},
	title={{Power and Plenty: Trade, War, and the World Economy in the Second Millennium}},
	author={Findlay, Ronald and O'Rourke, Kevin H.},
}

2. Add this reference to a text
3. go to design panel and look at the reference tooltip : no title whatever the style chosen

Observed behavior

no title appears whatever the style chosen

Screenshots

Desktop (please complete the following information):

• OS: linux mint
• Browser Firefox
• Version 76

Additional context
Add any other context about the problem here.