Spring MVC theme and locale error.

[LiomSV]

Hello. I am developing my first Spring project and I have some trouble.
I use Spring Tool Suite and standart Tomcat server.
I need two languages and two themes at my site. I do it this way

part of servlet-context.xml

<interceptors>          
        <beans:bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">  
            <beans:property name="paramName" value="lang" />  
        </beans:bean>
        <beans:bean class="org.springframework.web.servlet.theme.ThemeChangeInterceptor">   
            <beans:property name="paramName" value="theme" />
        </beans:bean>  
    </interceptors> 
	
	<beans:bean id="messageSource"  
        class="org.springframework.context.support.ReloadableResourceBundleMessageSource">  
        <beans:property name="basename" value="classpath:messages" />  
        <beans:property name="defaultEncoding" value="UTF-8" />  
    </beans:bean>   
  
    <beans:bean id="localeResolver"  
        class="org.springframework.web.servlet.i18n.CookieLocaleResolver" p:cookieName="localeResolver">  
        <beans:property name="defaultLocale" value="ru" />  
    </beans:bean>   
    
    <beans:bean class="org.springframework.ui.context.support.ResourceBundleThemeSource"
        id="themeSource"
        p:basenamePrefix="theme-" />
    
    <beans:bean class="org.springframework.web.servlet.theme.CookieThemeResolver"
        id="themeResolver"
        p:cookieName="themeResolver"
        p:defaultThemeName="standard" /

Here is one of theme-properties file (theme-standart.properties)

styleSheet=resources/css/bootstrap.css

one of messages-properties file (messages_en.properties)

login.welcome=Welcome!
login.login=Login
login.password=Password
login.signIn=Sign in
login.error=Invalid login or password!
login.registration=Registration
login.return=Come again

header.settings.en=English
header.settings.sp=Spain
header.settings.dark=Dark
header.settings.light=Light

And my error and the most mysterious thing

javax.servlet.jsp.JspTagException: Theme 'standard': No message found under code 'styleSheet' for locale 'en'

This error appears when I try open page at first time. I can add "?theme=dark" to the address line by myself and all will be fine and will work perfect(because theme-cookie will create).
But why and how are theme and locale connected? And how can I fix or avoid this error?