open excel files with umlauts on win works now

src/core/excelreader.cpp

@@ -1,16 +1,22 @@
 #include "excelreader.h"
 
 #include <xlnt/xlnt.hpp>
+#include <fstream>
 
 void ExcelReader::readSellersFromFile(const std::filesystem::path& filePath, Marketplace* market)
 {
+    xlnt::workbook wb;
+    std::ifstream mystream(filePath, std::ios::binary);
+    if(!mystream.is_open()) {
+	throw std::runtime_error("Could not open ecxel file");
+    }
+    wb.load(mystream);
+
     for (auto& seller : market->getSellers()) {
         seller->setState(Seller::State::DELETE);
     }
-    market->storeToDb(true);
 
-    xlnt::workbook wb;
+    market->storeToDb(true);
-    wb.load(filePath);
     auto ws = wb.sheet_by_index(0);
 
     const int START_ROW = 5;

src/gui/mainwindow.cpp

@@ -378,7 +378,7 @@ void MainWindow::onImportSellerExcelActionTriggered()
     if (filename.isEmpty())
         return;
     
-    std::filesystem::path filePath(filename.toStdU16String());
+    std::filesystem::path filePath(filename.toStdWString());
     
     ExcelReader::readSellersFromFile(filePath, marketplace_.get());
 }