Gave error dlg a description of the error for the user.

cockatrice/src/dlg_add_set_result.cpp

@@ -4,18 +4,19 @@
 #include <QPushButton>
 #include <QVBoxLayout>
 
-DlgAddSetResult::DlgAddSetResult(QWidget *parent, bool success) : QDialog(parent) {
+DlgAddSetResult::DlgAddSetResult(QWidget *parent, bool success, QString msg) : QDialog(parent) {
     status = new QLabel(this);
-    restart = new QLabel(this);
+    message = new QLabel(this);
 
     if (success) {
         setWindowTitle(tr("Success"));
         status->setText(QString("Sets/cards added to Cockatrice."));
-        restart->setText(QString("You must restart Cockatrice to use the new sets/cards."));
+        message->setText(QString("You must restart Cockatrice to use the new sets/cards."));
     }
     else {
         setWindowTitle(tr("Failed"));
         status->setText(QString("Sets/cards failed to import."));
+        message->setText(msg);
     }
 
     QDialogButtonBox *buttonBox = new QDialogButtonBox(this);
@@ -25,7 +26,7 @@ DlgAddSetResult::DlgAddSetResult(QWidget *parent, bool success) : QDialog(parent
 
     QVBoxLayout *parentLayout = new QVBoxLayout(this);
     parentLayout->addWidget(status);
-    parentLayout->addWidget(restart);
+    parentLayout->addWidget(message);
     parentLayout->addWidget(buttonBox);
 
     setLayout(parentLayout);

cockatrice/src/dlg_add_set_result.h

@@ -3,15 +3,16 @@
 
 #include <QDialog>
 #include <QLabel>
+#include <QString>
 
 class DlgAddSetResult : public QDialog {
 Q_OBJECT
 public:
-    DlgAddSetResult(QWidget *parent, bool success);
+    DlgAddSetResult(QWidget *parent, bool success, QString msg);
 private slots:
     void closeDialog();
 private:
-    QLabel *status, *restart;
+    QLabel *status, *message;
     QPushButton *ok;
 };
 

cockatrice/src/tab_deck_editor.cpp

@@ -885,16 +885,23 @@ void TabDeckEditor::actAddCustomSet()
     if (!dialog.exec())
         return;
 
+    QString fileName = dialog.selectedFiles().at(0);
+
+    if (!QFile::exists(fileName)) {
+        DlgAddSetResult dlg(this, false, QString("Selected file cannot be found."));
+        dlg.exec();
+        return;
+    }
+
     QDir dir(dataDir + "/customsets");
     int nextPrefix = getNextCustomSetPrefix(dir);
 
-    QString fileName = dialog.selectedFiles().at(0);
     bool res = QFile::copy(
         fileName, dir.absolutePath() + "/" + (nextPrefix > 9 ? "" : "0") +
         QString::number(nextPrefix) + "." + QFileInfo(fileName).fileName()
     );
 
-    DlgAddSetResult dlg(this, res);
+    DlgAddSetResult dlg(this, res, QString());
     dlg.exec();
 }