Fix crash with pointer to nil struct

pgtype/pgtype.go

@@ -952,7 +952,12 @@ func TryWrapStructScanPlan(target interface{}) (plan WrappedScanPlanNextSetter,
 		return nil, nil, false
 	}
 
-	targetElemValue := targetValue.Elem()
+	var targetElemValue reflect.Value
+	if targetValue.IsNil() {
+		targetElemValue = reflect.New(targetValue.Type().Elem())
+	} else {
+		targetElemValue = targetValue.Elem()
+	}
 	targetElemType := targetElemValue.Type()
 
 	if targetElemType.Kind() == reflect.Struct {

pgtype/pgtype_test.go

@@ -175,6 +175,15 @@ func TestTypeMapScanUnregisteredOIDToCustomType(t *testing.T) {
 	assert.Nil(t, pCt)
 }
 
+func TestTypeMapScanPointerToNilStructDoesNotCrash(t *testing.T) {
+	m := pgtype.NewMap()
+
+	type myStruct struct{}
+	var p *myStruct
+	err := m.Scan(0, pgx.TextFormatCode, []byte("(foo,bar)"), &p)
+	require.NotNil(t, err)
+}
+
 func TestTypeMapScanUnknownOIDTextFormat(t *testing.T) {
 	m := pgtype.NewMap()