fix shutdown crash after opening cross-folder virtual folder, 262492 sr=mscott

mailnews/base/src/nsMsgSearchDBView.cpp

@@ -83,6 +83,8 @@ NS_IMETHODIMP nsMsgSearchDBView::Close()
   for(PRInt32 i = 0; i < count; i++)
     m_dbToUseList[i]->RemoveListener(this);
 
+  m_dbToUseList.Clear();
+
   return NS_OK;
 }
 
@@ -222,6 +224,12 @@ nsMsgSearchDBView::OnNewSearch()
     return NS_OK;
 }
 
+NS_IMETHODIMP nsMsgSearchDBView::OnAnnouncerGoingAway(nsIDBChangeAnnouncer *instigator)
+{
+  m_dbToUseList.RemoveObject(NS_STATIC_CAST(nsIMsgDatabase *, instigator));
+  return nsMsgDBView::OnAnnouncerGoingAway(instigator);
+}
+
 nsresult nsMsgSearchDBView::GetFolders(nsISupportsArray **aFolders)
 {
   NS_ENSURE_ARG_POINTER(aFolders);

mailnews/base/src/nsMsgSearchDBView.h

@@ -67,6 +67,8 @@ public:
   virtual nsresult OnNewHeader(nsIMsgDBHdr *newHdr, nsMsgKey parentKey, PRBool ensureListed);
   NS_IMETHOD GetFolderForViewIndex(nsMsgViewIndex index, nsIMsgFolder **folder);
 
+  NS_IMETHOD OnAnnouncerGoingAway(nsIDBChangeAnnouncer *instigator);
+
   virtual nsresult GetFolders(nsISupportsArray **aFolders);
   virtual nsresult GetFolderFromMsgURI(const char *aMsgURI, nsIMsgFolder **aFolder);