https://github.com/wesnoth/wesnoth/commit/f6a32792d023d182d350b5a2ed9e469ad67484c8.patch
This should be able to be removed with wesnoth@1.14.6

From f6a32792d023d182d350b5a2ed9e469ad67484c8 Mon Sep 17 00:00:00 2001
From: Wedge009 <wedge009@wedge009.net>
Date: Thu, 27 Dec 2018 08:15:10 +1100
Subject: [PATCH] Use explicit casts to accommodate changes to boost's tribool
 in 1.69.

(fixes #3646)
---
 src/units/frame.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/units/frame.cpp b/src/units/frame.cpp
index 3215fa4fa79d..6370ad69566b 100644
--- a/src/units/frame.cpp
+++ b/src/units/frame.cpp
@@ -460,15 +460,15 @@ std::vector<std::string> frame_parsed_parameters::debug_strings() const
 	}
 
 	if(!boost::indeterminate(auto_vflip_)) {
-		v.emplace_back("auto_vflip=" + utils::bool_string(auto_vflip_));
+		v.emplace_back("auto_vflip=" + utils::bool_string(static_cast<bool>(auto_vflip_)));
 	}
 
 	if(!boost::indeterminate(auto_hflip_)) {
-		v.emplace_back("auto_hflip=" + utils::bool_string(auto_hflip_));
+		v.emplace_back("auto_hflip=" + utils::bool_string(static_cast<bool>(auto_hflip_)));
 	}
 
 	if(!boost::indeterminate(primary_frame_)) {
-		v.emplace_back("primary_frame=" + utils::bool_string(primary_frame_));
+		v.emplace_back("primary_frame=" + utils::bool_string(static_cast<bool>(primary_frame_)));
 	}
 
 	if(!drawing_layer_.get_original().empty()) {
@@ -768,7 +768,7 @@ const frame_parameters unit_frame::merge_parameters(int current_time, const fram
 	}
 
 	// Convert the tribool to bool
-	const bool primary = result.primary_frame == true || boost::logic::indeterminate(result.primary_frame);
+	const bool primary = static_cast<bool>(result.primary_frame) || boost::logic::indeterminate(result.primary_frame);
 
 	/** The engine provides a default image to use for the unit when none is available */
 	result.image = current_val.image.is_void() || current_val.image.get_filename().empty()
