[common] Fix deepMerge() as typeof null is object

 common.js

@@ -123,7 +123,7 @@
 **********/

function deepMerge(a1, a2) {
    if(typeof a1 !== 'object' || typeof a2 !== 'object') {
    if(a1 === null || typeof a1 !== 'object' || a2 === null || typeof a2 !== 'object') {
        return a2;
    }
    Object.keys(a2).forEach(function (key) {

 index.html

@@ -136,7 +136,7 @@
        </div>
        <script src="https://polyfill.io/v3/polyfill.min.js?features=Promise,XMLHttpRequest"></script>
        <script type="text/javascript" src="lang_pl.js?v11" id="lang_script"></script>
        <script type="text/javascript" src="common.js?v12"></script>
        <script type="text/javascript" src="common.js?v13"></script>
        <script type="text/javascript" src="index.js?v8"></script>
    </body>
</html>

 map.html

@@ -21,7 +21,7 @@
<script src="https://polyfill.io/v3/polyfill.min.js?features=Array.prototype.forEach,Array.prototype.includes,Array.prototype.map,Element.prototype.classList,Promise,String.prototype.startsWith,XMLHttpRequest,requestAnimationFrame"></script>
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.6.1/build/ol.js" integrity="sha384-2t8P2Mt0pPrLNwMqTljtykP6hpy7mzd34amfOqUYKK74XwsZgukowi3L4lW4bd3K" crossorigin="anonymous"></script>
<script tyle="text/javascript" src="lang_pl.js?v11" id="lang_script"></script>
<script tyle="text/javascript" src="common.js?v12"></script>
<script tyle="text/javascript" src="common.js?v13"></script>
<script tyle="text/javascript" src="map.js?v28"></script>
</body>
</html>