fix type issue in PropertyDescriptor

bbootimg/src/main/kotlin/avb/desc/PropertyDescriptor.kt

@@ -8,10 +8,10 @@ class PropertyDescriptor(
         var key: String = "",
         var value: String = "") : Descriptor(TAG, 0U, 0) {
     override fun encode(): ByteArray {
-        if (SIZE != Struct3(FORMAT_STRING).calcSize()) {
+        if (SIZE != Struct3(FORMAT_STRING).calcSize()!!.toUInt()) {
             throw RuntimeException()
         }
-        this.num_bytes_following = (SIZE + this.key.length + this.value.length + 2 - 16L).toULong()
+        this.num_bytes_following = (SIZE + this.key.length.toUInt() + this.value.length.toUInt() + 2U - 16U).toULong()
         val nbfWithPadding = Helper.round_to_multiple(this.num_bytes_following.toLong(), 8).toULong()
         val paddingSize = nbfWithPadding - num_bytes_following
         val padding = Struct3("${paddingSize}x").pack(0)
@@ -30,22 +30,22 @@ class PropertyDescriptor(
         val info = Struct3(FORMAT_STRING).unpack(data)
         this.tag = info[0] as ULong
         this.num_bytes_following = info[1] as ULong
-        val keySize = info[2] as Long
-        val valueSize = info[3] as Long
-        val expectedSize = Helper.round_to_multiple(SIZE - 16 + keySize + 1 + valueSize + 1, 8)
+        val keySize = (info[2] as ULong).toUInt()
+        val valueSize = (info[3] as ULong).toUInt()
+        val expectedSize = Helper.round_to_multiple(SIZE - 16U + keySize + 1U + valueSize + 1U, 8U)
         if (this.tag != TAG || expectedSize.toULong() != this.num_bytes_following) {
             throw IllegalArgumentException("Given data does not look like a |property| descriptor")
         }
         this.sequence = seq
 
         val info2 = Struct3("${keySize}sx${valueSize}s").unpack(data)
-        this.key = String(info2[0] as ByteArray)
-        this.value = String(info2[2] as ByteArray)
+        this.key = info2[0] as String
+        this.value = info2[2] as String
     }
 
     companion object {
         const val TAG: ULong = 0U
-        const val SIZE = 32
+        const val SIZE = 32U
         const val FORMAT_STRING = "!4Q"
     }
 }