do not assume source is an object

Otherwise `Reflect.ownKeys` would crash on non-object values.

Co-Authored-By: Jordan Pittman <thecrypticace@gmail.com>

packages/tailwindcss/src/compat/config/deep-merge.ts

@@ -17,7 +17,7 @@ export function deepMerge<T extends object>(
   type Value = T[Key]
 
   for (let source of sources) {
-    if (source === null || source === undefined) {
+    if (source === null || source === undefined || typeof source !== 'object') {
       continue
     }