fix 21909

previously we passed a temporary object and saved a reference to it in
unit_callable contructor. Leading to sefaults and undefined bahaviour.

src/callable_objects.hpp

@@ -143,8 +143,8 @@ class attack_type_callable : public game_logic::formula_callable {
 class unit_callable : public game_logic::formula_callable {
 public:
 	typedef map_location location;
-	unit_callable(const std::pair<location, unit>& pair)
-	  : loc_(pair.first), u_(pair.second)
+	unit_callable(const location& loc, const unit& u)
+		: loc_(loc), u_(u)
 	{
 		type_ = UNIT_C;
 	}

src/unit.cpp

@@ -1629,7 +1629,7 @@ bool unit::internal_matches_filter(const vconfig& cfg, const map_location& loc,
 	}
 	config::attribute_value cfg_formula = cfg["formula"];
 	if (!cfg_formula.blank()) {
-		const unit_callable callable(std::pair<map_location, unit>(loc,*this));
+		const unit_callable callable(loc,*this);
 		const game_logic::formula form(cfg_formula);
 		if(!form.evaluate(callable).as_bool()) {///@todo use formula_ai
 			return false;