Fix a crash when trying to copy-paste the background layer

Such layers usually have non-transparent default pixel, which
automatically needs an image for exact bounds calculation, which
doesn't exist for the detached layers.

The patch saves the copied area bounds on the construction
of mime data, much before the layers become detached.

BUG:458890,458857,458248,458941


(cherry picked from commit aac93758)

libs/ui/kis_mimedata.cpp

@@ -59,6 +59,12 @@ KisMimeData::KisMimeData(QList<KisNodeSP> nodes, KisImageSP image, bool forceCop
     , m_image(image)
 {
     Q_ASSERT(m_nodes.size() > 0);
+
+    KIS_SAFE_ASSERT_RECOVER_RETURN(image);
+
+    Q_FOREACH (KisNodeSP node, nodes) {
+        m_copiedBounds |= KisLayerUtils::recursiveTightNodeVisibleBounds(node);
+    }
 }
 
 void KisMimeData::deepCopyNodes()
@@ -95,15 +101,10 @@ QStringList KisMimeData::formats () const
     return f;
 }
 
-KisDocument *createDocument(QList<KisNodeSP> nodes, KisImageSP srcImage)
+KisDocument *createDocument(QList<KisNodeSP> nodes, KisImageSP srcImage, const QRect &copiedBounds)
 {
     KisDocument *doc = KisPart::instance()->createTemporaryDocument();
-    QRect rc;
-    Q_FOREACH (KisNodeSP node, nodes) {
-        if (node) {
-            rc |= node->exactBounds();
-        }
-    }
+    QRect rc = copiedBounds;
 
     QRect offset(0, 0, rc.width(), rc.height());
     rc |= offset;
@@ -139,9 +140,9 @@ KisDocument *createDocument(QList<KisNodeSP> nodes, KisImageSP srcImage)
     return doc;
 }
 
-QByteArray serializeToByteArray(QList<KisNodeSP> nodes, KisImageSP srcImage)
+QByteArray serializeToByteArray(QList<KisNodeSP> nodes, KisImageSP srcImage, const QRect &copiedBounds)
 {
-    QScopedPointer<KisDocument> doc(createDocument(nodes, srcImage));
+    QScopedPointer<KisDocument> doc(createDocument(nodes, srcImage, copiedBounds));
     QByteArray result = doc->serializeToNativeByteArray();
 
     // avoid a sanity check failure caused by the fact that the image outlives
@@ -168,7 +169,7 @@ QVariant KisMimeData::retrieveData(const QString &mimetype, QVariant::Type prefe
     if (mimetype == "application/x-qt-image") {
         KisConfig cfg(true);
 
-        QScopedPointer<KisDocument> doc(createDocument(m_nodes, m_image));
+        QScopedPointer<KisDocument> doc(createDocument(m_nodes, m_image, m_copiedBounds));
 
         return doc->image()->projection()->convertToQImage(cfg.displayProfile(QApplication::desktop()->screenNumber(qApp->activeWindow())),
                                                            KoColorConversionTransformation::internalRenderingIntent(),
@@ -176,7 +177,7 @@ QVariant KisMimeData::retrieveData(const QString &mimetype, QVariant::Type prefe
     }
     else if (mimetype == "application/zip") {
 
-        QByteArray ba = serializeToByteArray(m_nodes, m_image);
+        QByteArray ba = serializeToByteArray(m_nodes, m_image, m_copiedBounds);
         return ba;
 
     }

libs/ui/kis_mimedata.h

@@ -8,6 +8,7 @@
 #define KIS_MIMEDATA_H
 
 #include <QMimeData>
+#include <QRect>
 
 #include <kis_types.h>
 #include <kritaui_export.h>
@@ -111,6 +112,7 @@ private:
     QList<KisNodeSP> m_nodes;
     bool m_forceCopy;
     KisImageSP m_image;
+    QRect m_copiedBounds;
 };
 
 #endif // KIS_MIMEDATA_H