early return from embark_update during an active search to improve performance

- embark-assistant.cpp: checking if a search is active, if so return early

plugins/embark-assistant/embark-assistant.cpp

@@ -57,6 +57,12 @@ namespace embark_assist {
         //===============================================================================
 
         void embark_update() {
+            // not updating the embark overlay during an active find/match/survey phase
+            // which leads to better performance
+            if (state != nullptr && state->match_iterator.active) {
+                return;
+            }
+
             auto screen = Gui::getViewscreenByType<df::viewscreen_choose_start_sitest>(0);
             embark_assist::defs::mid_level_tiles mlt;
             embark_assist::survey::initiate(&mlt);