Fix: When destroying a component with an not initialized swiper

surmon-china#341

Author: DarkRiDDeR

src/ssr.js

@@ -112,7 +112,9 @@ const swiperDirective = globalOptions => {
       const instanceName = getInstanceName(el, binding, vnode);
       const swiper = vnode.context[instanceName];
       if (swiper) {
-        swiper.destroy && swiper.destroy();
+        if (swiper.destroy && swiper.initialized === true) {
+          swiper.destroy();
+        }
         delete vnode.context[instanceName];
       }
     }