add new tab only if was not already opened

src/store/index.js

@@ -70,11 +70,13 @@ export default new Vuex.Store({
       state.dbName = name
     },
     addTab (state, tab) {
+      // add new tab only if was not already opened
+      if (!state.tabs.some(openedTab => openedTab.id === tab.id)) {
         state.tabs.push(tab)
-
         if (!tab.name) {
           state.untitledLastIndex += 1
         }
+      }
     },
     updateTab (state, { index, name, id, query, chart, isUnsaved }) {
       const tab = state.tabs[index]