Fix compilation warnings about QFile::open

src/libneochat/neochatconnection.cpp

@@ -533,7 +533,11 @@ KeyImport::Error NeoChatConnection::exportMegolmSessions(const QString &passphra
     }
     QUrl url(path);
     QFile file(url.toLocalFile());
-    file.open(QFile::WriteOnly);
+    auto ok = file.open(QFile::WriteOnly);
+    if (!ok) {
+        qWarning() << "Failed to open" << file.fileName() << file.errorString();
+        return KeyImport::OtherError;
+    }
     file.write(result.value());
     file.close();
     return KeyImport::Success;

src/libneochat/neochatroom.cpp

@@ -261,7 +261,10 @@ QCoro::Task<void> NeoChatRoom::doUploadFile(QUrl url, QString body, std::optiona
 
         QTemporaryFile file;
         file.setFileTemplate(QStringLiteral("XXXXXX.jpg"));
-        file.open();
+        auto ok = file.open();
+        if (!ok) {
+            qWarning() << "Failed to open" << file.fileName() << file.errorString();
+        }
 
         const auto thumbnailImage = sink.videoFrame().toImage();
         Q_UNUSED(thumbnailImage.save(file.fileName()))