From fcdd6183312e64ff52dd8298f9ee512a378acd25 Mon Sep 17 00:00:00 2001
From: Geoff Hutchison <geoff.hutchison@gmail.com>
Date: Tue, 7 Jan 2025 14:58:32 -0500
Subject: [PATCH] Be more careful in forcefield setup

Signed-off-by: Geoff Hutchison <geoff.hutchison@gmail.com>
---
 avogadro/qtplugins/forcefield/forcefield.cpp | 28 ++++++++++++++++----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/avogadro/qtplugins/forcefield/forcefield.cpp b/avogadro/qtplugins/forcefield/forcefield.cpp
index ce779507ae..85a0b426b5 100644
--- a/avogadro/qtplugins/forcefield/forcefield.cpp
+++ b/avogadro/qtplugins/forcefield/forcefield.cpp
@@ -207,6 +207,9 @@ void Forcefield::setMolecule(QtGui::Molecule* mol)
 
 void Forcefield::setupMethod()
 {
+  if (m_molecule == nullptr)
+    return; // nothing to do until its set
+
   if (m_autodetect)
     m_methodName = recommendedForceField();
 
@@ -234,15 +237,20 @@ void Forcefield::setupMethod()
     delete m_method; // delete the previous one
     m_method = Calc::EnergyManager::instance().model(m_methodName);
   }
-
-  m_method->setMolecule(m_molecule);
+  if (m_method != nullptr)
+    m_method->setMolecule(m_molecule);
 }
 
 void Forcefield::optimize()
 {
-  if (m_molecule == nullptr || m_method == nullptr)
+  if (m_molecule == nullptr)
     return;
 
+  if (m_method == nullptr)
+    setupMethod();
+  if (m_method == nullptr)
+    return; // bad news
+
   if (!m_molecule->atomCount()) {
     QMessageBox::information(nullptr, tr("Avogadro"),
                              tr("No atoms provided for optimization"));
@@ -375,9 +383,14 @@ void Forcefield::optimize()
 
 void Forcefield::energy()
 {
-  if (m_molecule == nullptr || m_method == nullptr)
+  if (m_molecule == nullptr)
     return;
 
+  if (m_method == nullptr)
+    setupMethod();
+  if (m_method == nullptr)
+    return; // bad news
+
   int n = m_molecule->atomCount();
   // we have to cast the current 3d positions into a VectorXd
   Core::Array<Vector3> pos = m_molecule->atomPositions3d();
@@ -395,9 +408,14 @@ void Forcefield::energy()
 
 void Forcefield::forces()
 {
-  if (m_molecule == nullptr || m_method == nullptr)
+  if (m_molecule == nullptr)
     return;
 
+  if (m_method == nullptr)
+    setupMethod();
+  if (m_method == nullptr)
+    return; // bad news
+
   int n = m_molecule->atomCount();
 
   // double-check the mask