Fix #10987: Double-close of dropdown stopped land-info tool working as default. (#11000)

Clicking and releasing on the query toolbar icon is meant to select the land-info tool.

This did not work as during closing a window, OnFocusLost() is called, which then closes the window again. These two calls toggled the land-info tool one and off in the same action.

Resolve by not calling Window::Close in OnFocusLost() if the window is already closing.

src/widgets/dropdown.cpp

@@ -197,9 +197,9 @@ struct DropdownWindow : Window {
 		if (nwc != nullptr) SetBit(nwc->disp_flags, NDB_DROPDOWN_CLOSED);
 	}
 
-	void OnFocusLost() override
+	void OnFocusLost(bool closing) override
 	{
-		this->Close();
+		if (!closing) this->Close();
 	}
 
 	Point OnInitialPosition(int16 sm_width, int16 sm_height, int window_number) override