Field calculator: provide a list of default field types

in case the provider does not (WFS is one of them).

Rationale: consider that there is not such
a thing like a list of supported types for WFS
and parsing the particular describeFeatureType
for the layer would restrict the types to only
those actually existing in the layer, but
we are dealing with virtual fields here (because
WFS has no column add capabilities) so
let's give the users a minimal set of useful
types to play with.

Fixes #21086

src/app/qgsfieldcalculator.cpp

@@ -348,7 +348,17 @@ void QgsFieldCalculator::populateOutputFieldTypes()
   }
 
   mOutputFieldTypeComboBox->blockSignals( true );
-  const QList< QgsVectorDataProvider::NativeType > &typelist = provider->nativeTypes();
+
+  // Not all providers have a native types list (WFS), provide default
+  // Integer|Real|Character|Date|Boolean
+  const QList< QgsVectorDataProvider::NativeType > &typelist { provider->nativeTypes().isEmpty() ? ( QList< QgsVectorDataProvider::NativeType >()
+      << QgsVectorDataProvider::NativeType( tr( "Whole number (integer)" ), QStringLiteral( "integer" ), QVariant::Int, 0, 10 )
+      << QgsVectorDataProvider::NativeType( tr( "Decimal number (double)" ), QStringLiteral( "double precision" ), QVariant::Double, -1, -1, -1, -1 )
+      << QgsVectorDataProvider::NativeType( tr( "Text (string)" ), QStringLiteral( "string" ), QVariant::String )
+      << QgsVectorDataProvider::NativeType( tr( "Date" ), QStringLiteral( "date" ), QVariant::Date, -1, -1, -1, -1 )
+      << QgsVectorDataProvider::NativeType( tr( "Boolean (bool)" ), QStringLiteral( "bool" ),  QVariant::Bool ) )
+      :  provider->nativeTypes() };
+
   for ( int i = 0; i < typelist.size(); i++ )
   {
     mOutputFieldTypeComboBox->addItem( typelist[i].mTypeDesc );