Fix crash when pressing mouse button and selecting different rss items

src/rss_imp.cpp

@@ -460,13 +460,13 @@ void RSSImp::refreshNewsList(QTreeWidgetItem* item) {
 void RSSImp::refreshTextBrowser() {
   QList<QTreeWidgetItem*> selection = listNews->selectedItems();
   if(selection.empty()) return;
+  Q_ASSERT(selection.size() == 1);
   QTreeWidgetItem *item = selection.first();
   if(item == previous_news) return;
   // Stop displaying previous news if necessary
   if(listStreams->currentFeed() == listStreams->getUnreadItem()) {
     if(previous_news) {
-      delete previous_news;
+      delete listNews->takeTopLevelItem(listNews->indexOfTopLevelItem(previous_news));
-      previous_news = 0;
     }
     previous_news = item;
   }

src/ui/rss.ui

@@ -125,7 +125,10 @@ p, li { white-space: pre-wrap; }
            <enum>Qt::CustomContextMenu</enum>
           </property>
           <property name="selectionMode">
-           <enum>QAbstractItemView::ExtendedSelection</enum>
+           <enum>QAbstractItemView::SingleSelection</enum>
+          </property>
+          <property name="selectionBehavior">
+           <enum>QAbstractItemView::SelectItems</enum>
           </property>
           <property name="rootIsDecorated">
            <bool>false</bool>
@@ -136,6 +139,15 @@ p, li { white-space: pre-wrap; }
           <property name="allColumnsShowFocus">
            <bool>true</bool>
           </property>
+          <property name="expandsOnDoubleClick">
+           <bool>false</bool>
+          </property>
+          <attribute name="headerVisible">
+           <bool>false</bool>
+          </attribute>
+          <attribute name="headerStretchLastSection">
+           <bool>true</bool>
+          </attribute>
           <attribute name="headerVisible">
            <bool>false</bool>
           </attribute>