overwrite invalid input strings

GUI/View/Numeric/DoubleSpinBox.cpp

@@ -70,8 +70,10 @@ QAbstractSpinBox::StepEnabled DoubleSpinBox::stepEnabled() const
 double DoubleSpinBox::fromDisplay() const
 {
     double result;
-    ASSERT(Base::String::to_double(lineEdit()->text().toStdString(), &result));
-    return result;
+    if (Base::String::to_double(lineEdit()->text().toStdString(), &result))
+        return result;
+    // invalid input => restore last valid value
+    return m_valueProperty.value();
 }
 
 void DoubleSpinBox::setValue(double val)