Fix missing import in generation

imports.go

@@ -157,12 +157,16 @@ var defaultTemplateImports = imports{
 
 var defaultSingletonTemplateImports = map[string]imports{
 	"boil_helpers": {
-		standard: importList{},
 		thirdParty: importList{
 			`"github.com/vattle/sqlboiler/boil"`,
 			`"github.com/vattle/sqlboiler/boil/qm"`,
 		},
 	},
+	"boil_types": {
+		thirdParty: importList{
+			`"github.com/pkg/errors"`,
+		},
+	},
 }
 
 var defaultTestTemplateImports = imports{