Swap error before setting to prevent nil error

Test: go test soong tests
Change-Id: Ib6e3519f0f596b3699882fe682e648dd69ed5645
diff --git a/android/soong_config_modules.go b/android/soong_config_modules.go
index c0f4523..c1e92b8 100644
--- a/android/soong_config_modules.go
+++ b/android/soong_config_modules.go
@@ -382,15 +382,15 @@
 		defer r.Close()
 
 		mtDef, errs := soongconfig.Parse(r, from)
-		if ctx.Config().BuildMode == Bp2build {
-			ctx.Config().Bp2buildSoongConfigDefinitions.AddVars(*mtDef)
-		}
-
 		if len(errs) > 0 {
 			reportErrors(ctx, from, errs...)
 			return (map[string]blueprint.ModuleFactory)(nil)
 		}
 
+		if ctx.Config().BuildMode == Bp2build {
+			ctx.Config().Bp2buildSoongConfigDefinitions.AddVars(*mtDef)
+		}
+
 		globalModuleTypes := ctx.moduleFactories()
 
 		factories := make(map[string]blueprint.ModuleFactory)