From f19aac18a2f7997583395e91800f85cd04425233 Mon Sep 17 00:00:00 2001
From: juha <juha@lazarus-ide.org>
Date: Sun, 4 Jul 2021 11:42:45 +0000
Subject: [PATCH] SqlDb: Prevent a crash when dropping TPQTEventMonitor on a
 form. Issue #39134, patch by CudaText man.

git-svn-id: trunk@65359 -
---
 components/sqldb/pqteventmonitor.pas | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/components/sqldb/pqteventmonitor.pas b/components/sqldb/pqteventmonitor.pas
index 19e65c8124..83e7551812 100644
--- a/components/sqldb/pqteventmonitor.pas
+++ b/components/sqldb/pqteventmonitor.pas
@@ -14,6 +14,7 @@ type
 
   TPQTEventMonitor=class(TPQEventMonitor)
   private
+    FInited:Boolean;
     Timer:TTimer;
     function GetPollInterval: integer;
     procedure OnTimer(Sender: TObject);
@@ -34,7 +35,6 @@ implementation
 
 procedure TPQTEventMonitor.SetPollInterval(AValue: integer);
 begin
-  if Timer.Interval=AValue then Exit;
   Timer.Interval:=AValue;
 end;
 
@@ -50,8 +50,14 @@ end;
 
 constructor TPQTEventMonitor.Create(AOwner: TComponent);
 begin
-  inherited Create(AOwner);
-  Timer:=TTImer.Create(self);
+  try
+    inherited Create(AOwner);
+    FInited:=true;
+  except
+    //FPC code raises EInOutError in Create() if Postgres lib was not loaded
+    FInited:=false;
+  end;
+  Timer:=TTimer.Create(self);
   Timer.Interval:=500;
   Timer.Enabled:=false;
   Timer.OnTimer:=@OnTimer;
@@ -59,17 +65,20 @@ end;
 
 destructor TPQTEventMonitor.Destroy;
 begin
+  if not FInited then exit;
   inherited Destroy;
 end;
 
 procedure TPQTEventMonitor.RegisterEvents;
 begin
+  if not FInited then exit;
   inherited RegisterEvents;
   Timer.Enabled:=true;
 end;
 
 procedure TPQTEventMonitor.UnRegisterEvents;
 begin
+  if not FInited then exit;
   Timer.Enabled:=false;
   inherited UnRegisterEvents;
 end;