Fix minimap disappearing

[mikkohei13]

Repro:

• Go to Vihko trip form
• Add an unit
• Add location for the unit
• Hover mouse over the map icon on the unit row

Expected:

• Small map stays displayed as long as mouse cursor is on the map icon

Actual:

• Small map appears for a fraction of a second, then disappears

Firefox 151 on macOS.