Address some build warnings

app/src/main/java/eu/kanade/tachiyomi/util/storage/DiskUtil.kt

@@ -21,7 +21,7 @@ object DiskUtil {
     fun getDirectorySize(f: File): Long {
         var size: Long = 0
         if (f.isDirectory) {
-            for (file in f.listFiles()) {
+            for (file in f.listFiles().orEmpty()) {
                 size += getDirectorySize(file)
             }
         } else {

app/src/main/java/eu/kanade/tachiyomi/util/storage/OkioExtensions.kt

@@ -14,7 +14,7 @@ import java.io.OutputStream
 fun BufferedSource.saveTo(file: File) {
     try {
         // Create parent dirs if needed
-        file.parentFile.mkdirs()
+        file.parentFile?.mkdirs()
 
         // Copy to destination
         saveTo(file.outputStream())

app/src/main/java/eu/kanade/tachiyomi/util/system/IntentExtensions.kt

@@ -4,12 +4,12 @@ import android.content.ClipData
 import android.content.Intent
 import android.net.Uri
 
-fun Uri.toShareIntent(): Intent {
+fun Uri.toShareIntent(type: String = "image/*"): Intent {
     val uri = this
     return Intent(Intent.ACTION_SEND).apply {
         putExtra(Intent.EXTRA_STREAM, uri)
         clipData = ClipData.newRawUri(null, uri)
-        type = "image/*"
+        setType(type)
         flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_GRANT_READ_URI_PERMISSION
     }
 }