Close attachment_iodevice after reading the picture.

This is essential to end the transaction opened to fetch
the large object.

src/attachment.cpp

@@ -1061,6 +1061,14 @@ attachment_iodevice::~attachment_iodevice()
 {
 }
 
+void
+attachment_iodevice::close()
+{
+  if (m_a != NULL)
+    m_a->close();		// ends database transaction
+  QIODevice::close();
+}
+
 qint64
 attachment_iodevice::readData(char* data, qint64 size)
 {
@@ -1102,6 +1110,7 @@ attachment_iodevice::isSequential() const
 void
 attachment_iodevice::abort()
 {
+  if (m_a != NULL)
   m_a->close();
 }
 

src/attachment.h

@@ -186,11 +186,12 @@ class attachment_iodevice: public QIODevice
   qint64 readData(char* data, qint64 size);
   qint64 writeData(const char* data, qint64 maxsize);
   void abort();
+  void close();
   qint64 bytesAvailable() const;
   bool atEnd() const;
   bool isSequential() const;
 private:
-  attachment* m_a;
+  attachment* m_a = NULL;
   int already_read;
 private slots:
   void go();

src/image_viewer.cpp

@@ -70,6 +70,7 @@ image_viewer::show_attachment(attachment* a)
   imgr.setAutoTransform(true);
 #endif
   m_image = imgr.read();
+  io.close();			// ends transaction
 
   if (m_image.isNull()) {
     QMessageBox::critical(this, APP_NAME, tr("Cannot instantiate image from attachment"));
@@ -88,7 +89,7 @@ image_viewer::show_attachment(attachment* a)
 
     m_image_label->resize(m_scale_factor * m_image_label->pixmap()->size());
     show();
- }
+  }
 }
 
 image_label::image_label(QWidget* parent) : QLabel(parent)