Refactor to use takeUnless

Author: lauzadis

aws-crt-kotlin/native/src/aws/sdk/kotlin/crt/io/MutableBufferNative.kt

@@ -91,11 +91,9 @@ private sealed interface InnerBuffer {
         init {
             pointer.pointed.len = 0.convert()
             pointer.pointed.capacity = dest.size.convert()
-            pointer.pointed.buffer = if (dest.isNotEmpty()) {
-                pinned.addressOf(0).reinterpret()
-            } else {
-                null
-            }
+            pointer.pointed.buffer =  pinned.takeUnless { dest.isEmpty() }
+                ?.addressOf(0)
+                ?.reinterpret()
         }
 
         override fun release() {