gui: mainwindow: Only trigger preview generation when in tab

Indirectly generation would fire when we set combobox index
programitcally. So it's slot should only trigger the generation
when the user is viewing the preview tab

gui/mainwindow.cpp

@@ -198,7 +198,14 @@ void MainWindow::connectSignals()
 	connect(ui->btnSaveSettings, &QPushButton::clicked, this, &MainWindow::saveSettings);
 	connect(ui->btnOpenFailed, &QPushButton::clicked, this, &MainWindow::exportFailedPaths);
 	connect(
-		ui->comboPreviewFiles, qOverload<int>(&QComboBox::currentIndexChanged), this, [&]() { makePreviews(1); },
+		ui->comboPreviewFiles, qOverload<int>(&QComboBox::currentIndexChanged), this,
+		[&]()
+		{
+			if(this->previewTabActive())
+			{
+				makePreviews(1);
+			}
+		},
 		Qt::QueuedConnection);
 	connect(&ipcPreviewClient, &IPCPreviewClient::previewReceived, this, &MainWindow::previewReceived,
 			Qt::QueuedConnection);