fix: suppress terser warning if minify disabled (#15275)

Author: bluwy

packages/vite/src/node/config.ts

@@ -821,7 +821,11 @@ export async function resolveConfig(
 
   // validate config
 
-  if (config.build?.terserOptions && config.build.minify !== 'terser') {
+  if (
+    config.build?.terserOptions &&
+    config.build.minify &&
+    config.build.minify !== 'terser'
+  ) {
     logger.warn(
       colors.yellow(
         `build.terserOptions is specified but build.minify is not set to use Terser. ` +