undefined checks in database transactions

src/app/database/database-connection.js

@@ -3,6 +3,7 @@ import * as SQLite from "expo-sqlite";
 function openDatabase() {
   const db = SQLite.openDatabase("db.testDb");
 
+  // return undefined
   return db;
 }
 

src/app/database/database-init.js

@@ -28,7 +28,7 @@ function createAllTables(db) {
  *
  */
 function initDatabase(db) {
-  createAllTables(db);
+  (db != undefined && db !== null) && createAllTables(db);
 }
 
 export default initDatabase;

src/app/hooks/selectFromDB.js

@@ -140,9 +140,14 @@ function parseResult(db_result, parseRow) {
   return warnings;
 }
 
+function isAvailable(dataBase) {
+  return dataBase !== undefined && dataBase !== null;
+}
+
 function genericSelect(queriesToParsersMapper, dispatch, isFocused) {
   useEffect(() => {
     console.log("requesting data");
+    if (isAvailable(global.userDataBase)) {
       queriesToParsersMapper.forEach(([query, parser]) => {
         global.userDataBase.transaction((tx) => {
           tx.executeSql(query, [], (tx, results) => {
@@ -150,6 +155,7 @@ function genericSelect(queriesToParsersMapper, dispatch, isFocused) {
           });
         });
       });
+    }
   }, [isFocused]);
 }