Reset cached price when currency changes

Author: D-32

BitStore/Helper/ExchangeHelper.m

@@ -54,6 +54,7 @@ - (void)changeCurreny:(NSString *)currency {
     // update shared user
     SharedUser* user = [UserDefaults instance].sharedUser;
     user.todayCurrency = currency;
+    user.cachedPrice = nil;
     [UserDefaults instance].sharedUser = user;
 
     [self storeState];