fix highlighting everything on strchoice page left/right

src/dialogxml/dialogs/strchoice.cpp

@@ -256,6 +256,7 @@ void cStringChoice::clearHighlights() {
 
 bool cStringChoice::highlightSearch() {
 	bool match_on_page = false;
+	if(search_str.empty()) return false;
 
 	for(int offset = 0; offset < per_page; ++offset){
 		std::string led_id = "led" + std::to_string(offset + 1);