Don't allow accidentally searching for old terms after deleting searches

uhh basically if you search, get results, and then delete the search, press enter, then search again but find no results it was possible to have the results be the results from the first search instead of something that makes a little more sense

src/Etterna/Actor/Menus/MusicWheel.cpp

@@ -205,6 +205,7 @@ MusicWheel::ReloadSongList(bool searching, RString findme)
 	// when cancelling a search stay in the pack of your match... this should be
 	// more intuitive and relevant behavior -mina
 	if (findme == "" && lastvalidsearch != "") {
+		lastvalidsearch = "";
 		m_WheelItemDatasStatus[GAMESTATE->m_SortOrder] = INVALID;
 		readyWheelItemsData(GAMESTATE->m_SortOrder, false, findme);
 		SetOpenSection(m_sExpandedSectionName);