Fix compilation errors

Author: Isira-Seneviratne

app/src/main/java/org/schabi/newpipe/player/mediabrowser/PackageValidator.kt

@@ -146,21 +146,19 @@ internal class PackageValidator(context: Context) {
      */
     private fun buildCallerInfo(callingPackage: String): CallerPackageInfo? {
         val packageInfo = getPackageInfo(callingPackage) ?: return null
+        val applicationInfo = packageInfo.applicationInfo ?: return null
 
-        val appName = packageInfo.applicationInfo.loadLabel(packageManager).toString()
-        val uid = packageInfo.applicationInfo.uid
+        val appName = applicationInfo.loadLabel(packageManager).toString()
+        val uid = applicationInfo.uid
         val signature = getSignature(packageInfo)
 
-        val requestedPermissions = packageInfo.requestedPermissions
-        val permissionFlags = packageInfo.requestedPermissionsFlags
-        val activePermissions = mutableSetOf<String>()
-        requestedPermissions?.forEachIndexed { index, permission ->
-            if (permissionFlags[index] and REQUESTED_PERMISSION_GRANTED != 0) {
-                activePermissions += permission
-            }
-        }
+        val requestedPermissions = packageInfo.requestedPermissions?.asSequence().orEmpty()
+        val permissionFlags = packageInfo.requestedPermissionsFlags?.asSequence().orEmpty()
+        val activePermissions = (requestedPermissions zip permissionFlags)
+            .filter { (_, flag) -> flag and REQUESTED_PERMISSION_GRANTED != 0 }
+            .mapTo(mutableSetOf()) { (permission, _) -> permission }
 
-        return CallerPackageInfo(appName, callingPackage, uid, signature, activePermissions.toSet())
+        return CallerPackageInfo(appName, callingPackage, uid, signature, activePermissions)
     }
 
     /**
@@ -188,15 +186,16 @@ internal class PackageValidator(context: Context) {
      * returns `null` as the signature.
      */
     @Suppress("deprecation")
-    private fun getSignature(packageInfo: PackageInfo): String? =
-        if (packageInfo.signatures == null || packageInfo.signatures.size != 1) {
+    private fun getSignature(packageInfo: PackageInfo): String? {
+        val signatures = packageInfo.signatures
+        return if (signatures == null || signatures.size != 1) {
             // Security best practices dictate that an app should be signed with exactly one (1)
             // signature. Because of this, if there are multiple signatures, reject it.
             null
         } else {
-            val certificate = packageInfo.signatures[0].toByteArray()
-            getSignatureSha256(certificate)
+            getSignatureSha256(signatures[0].toByteArray())
         }
+    }
 
     /**
      * Finds the Android platform signing key signature. This key is never null.