#14178 Fix crash in slider editor from re-entrant field write

The integer slider editor cross-updated the spin box and slider without blocking signals, so a single user interaction wrote to the PDM field twice. The first (nested) write could trigger a field-changed callback that rebuilt the property panel and destroyed the spin box internal line edit, after which the second write dereferenced the dangling line edit in QAbstractSpinBox::text() and crashed.

Block the other widget signals while programmatically syncing in slotSliderValueChanged and updateSliderPosition, restoring the previous blocked state so it nests safely with configureAndUpdateUi. Add null guards in updateSliderPosition and writeValueToField.

Fwk/AppFwk/cafUserInterface/cafPdmUiSliderEditor.cpp

@@ -151,7 +151,14 @@ QWidget* PdmUiSliderEditor::createEditorWidget( QWidget* parent )
 //--------------------------------------------------------------------------------------------------
 void PdmUiSliderEditor::slotSliderValueChanged( int position )
 {
-    m_spinBox->setValue( position );
+    if ( m_spinBox )
+    {
+        // Block signals to avoid re-entering slotSpinBoxValueChanged(), which would write to the
+        // field a second time and may tear down this editor's widgets while we are still executing.
+        bool wasBlocked = m_spinBox->blockSignals( true );
+        m_spinBox->setValue( position );
+        m_spinBox->blockSignals( wasBlocked );
+    }
 
     writeValueToField();
 }
@@ -171,6 +178,8 @@ void PdmUiSliderEditor::slotSpinBoxValueChanged( int spinBoxValue )
 //--------------------------------------------------------------------------------------------------
 void PdmUiSliderEditor::updateSliderPosition()
 {
+    if ( m_spinBox.isNull() || m_slider.isNull() ) return;
+
     QString textValue = m_spinBox->text();
 
     bool convertOk      = false;
@@ -178,7 +187,12 @@ void PdmUiSliderEditor::updateSliderPosition()
     if ( convertOk )
     {
         newSliderValue = qBound( m_attributes.m_minimum, newSliderValue, m_attributes.m_maximum );
+
+        // Block signals to avoid re-entering slotSliderValueChanged(), which would write to the
+        // field a second time and may tear down this editor's widgets while we are still executing.
+        bool wasBlocked = m_slider->blockSignals( true );
         m_slider->setValue( newSliderValue );
+        m_slider->blockSignals( wasBlocked );
     }
 }
 
@@ -187,6 +201,8 @@ void PdmUiSliderEditor::updateSliderPosition()
 //--------------------------------------------------------------------------------------------------
 void PdmUiSliderEditor::writeValueToField()
 {
+    if ( m_spinBox.isNull() ) return;
+
     QString  textValue = m_spinBox->text();
     QVariant v;
     v = textValue;