Make sure any alternate unit is selected properly on movement+attack

src/mouse_events.cpp

@@ -609,11 +609,17 @@ void mouse_handler::move_action(bool browse)
 					save_whiteboard_attack(attack_from, hex, choice);
 				}
 				else if ( move_unit_along_current_route() ) {
+					bool alt_unit_selected = (selected_hex_ != src);
+					src = selected_hex_;
 					// clear current unit selection so that any other unit selected
 					// triggers a new selection
 					selected_hex_ = map_location();
-
+					
 					attack_enemy(attack_from, hex, choice); // Fight !!
+					if (alt_unit_selected && !selected_hex_.valid()) {
+						//reselect other unit if selected during movement animation
+						select_hex(src, browse);
+					}
 				}
 				//TODO: Maybe store the attack choice so "press t to continue"
 				//      can also continue the attack?