From 42a2f134643d2923f78f9e7980e887a49f0cfe88 Mon Sep 17 00:00:00 2001
From: Ben Ellis <benx45h@gmail.com>
Date: Tue, 21 Jul 2020 14:52:48 +0000
Subject: [PATCH] Added a check that sexprs isn't empty before popping

This fixes a crash on malformed sexprs in the DRC rules panel
---
 pcbnew/dialogs/panel_setup_rules.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pcbnew/dialogs/panel_setup_rules.cpp b/pcbnew/dialogs/panel_setup_rules.cpp
index 40b7446c68..7640419b2b 100644
--- a/pcbnew/dialogs/panel_setup_rules.cpp
+++ b/pcbnew/dialogs/panel_setup_rules.cpp
@@ -114,7 +114,9 @@ void PANEL_SETUP_RULES::onScintillaCharAdded( wxStyledTextEvent &aEvent )
         }
         else if( c == ')' )
         {
-            sexprs.pop();
+            if( !sexprs.empty() )
+                sexprs.pop();
+
             context = NONE;
         }
         else if( c == ' ' )