From 2d015bc75ac8ee957d1be77388a10d46ec7796ff Mon Sep 17 00:00:00 2001
From: Ansgar Becker <ansgarbecker@users.noreply.github.com>
Date: Thu, 21 Oct 2010 22:01:41 +0000
Subject: [PATCH] Fix EStringListError when disconnecting from a server with
 many databases, having the ListDatabases open, and switching to a server with
 less databases. See http://www.heidisql.com/forum.php?t=6594

---
 source/main.pas | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/source/main.pas b/source/main.pas
index 39e0953d..6136d69e 100644
--- a/source/main.pas
+++ b/source/main.pas
@@ -6602,6 +6602,7 @@ end;
 procedure TMainForm.DBtreeFocusChanged(Sender: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex);
 var
   DBObj, PrevDBObj: PDBObject;
+  MainTabToActivate: TTabSheet;
 begin
   if not Assigned(Node) then begin
     LogSQL('DBtreeFocusChanged without node.', lcDebug);
@@ -6613,13 +6614,16 @@ begin
   if Assigned(DataGridResult) and DataGridResult.Modified then
     actDataPostChangesExecute(DataGrid);
 
+  // Set wanted main tab and call SetMainTab later, when all lists have been invalidated
+  MainTabToActivate := nil;
+
   DBObj := Sender.GetNodeData(Node);
 
   case DBObj.NodeType of
 
     lntNone: begin
       if (not DBtree.Dragging) and (not QueryTabActive) then
-        SetMainTab(tabHost);
+        MainTabToActivate := tabHost;
       tabDatabase.TabVisible := False;
       tabEditor.TabVisible := False;
       tabData.TabVisible := False;
@@ -6637,7 +6641,7 @@ begin
         end;
       end;
       if (not DBtree.Dragging) and (not QueryTabActive) then
-        SetMainTab(tabDatabase);
+        MainTabToActivate := tabDatabase;
       tabDatabase.TabVisible := True;
       tabEditor.TabVisible := False;
       tabData.TabVisible := False;
@@ -6662,7 +6666,7 @@ begin
         // When a table is clicked in the tree, and the current
         // tab is a Host or Database tab, switch to showing table columns.
         if (PagecontrolMain.ActivePage = tabHost) or (PagecontrolMain.ActivePage = tabDatabase) then
-          SetMainTab(tabEditor);
+          MainTabToActivate := tabEditor;
         if DataGrid.Tag = VTREE_LOADED then
           InvalidateVT(DataGrid, VTREE_NOTLOADED_PURGECACHE, False);
         // Update the list of columns
@@ -6696,9 +6700,11 @@ begin
   SetLength(FTreeClickHistory, Length(FTreeClickHistory)+1);
   FTreeClickHistory[Length(FTreeClickHistory)-1] := Node;
 
-
+  // Main tab stuff
   tabHost.Caption := 'Host: '+sstr(DBObj.Connection.Parameters.HostName, 20);
   tabDatabase.Caption := 'Database: '+sstr(DBObj.Connection.Database, 20);
+  SetMainTab(MainTabToActivate);
+
   DBTree.InvalidateColumn(0);
   FixQueryTabCloseButtons;
   SetWindowCaption;
@@ -8983,7 +8989,7 @@ end;
 procedure TMainForm.SetMainTab(Page: TTabSheet);
 begin
   // Safely switch main tab
-  if not FTreeRefreshInProgress then begin
+  if (Page <> nil) and (not FTreeRefreshInProgress) then begin
     PagecontrolMain.ActivePage := Page;
     PageControlMain.OnChange(Page);
   end;