fix: fix ArrayStoreException

Close #170

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/gridexporter/CsvStreamResourceWriter.java

@@ -60,7 +60,7 @@ public void accept(OutputStream out, VaadinSession session) throws IOException {
           .filter(this::isExportable)
           .collect(Collectors.toList()));
 
-      headers = getGridHeaders(grid).stream().map(GridHeader::getTexts).toArray(String[]::new);
+      headers = getGridHeaders(grid).stream().map(GridHeader::getText).toArray(String[]::new);
       data = obtainDataStream(grid.getDataProvider())
           .map(this::buildRow)
           .collect(Collectors.toList());