feat(spoof): skip absent boot-lock props

Creating a vendor-specific boot prop on a device that never had
one is itself a detection signal. Existence-guard the four
boot-lock targets so absent props stay absent.

app/src/main/java/org/matrix/TEESimulator/config/BootStateManager.kt

@@ -16,6 +16,10 @@ object BootStateManager {
     fun apply() {
         for ((name, target) in targets) {
             val current = SystemProperties.get(name, "")
+            if (current.isEmpty()) {
+                SystemLogger.debug("BootStateManager: $name absent on this device, skip")
+                continue
+            }
             if (current == target) {
                 SystemLogger.debug("BootStateManager: $name already $target, skip")
                 continue