fix file size parsing issue causing crash

Opening a PDF using Storage Access Framework (SAF) causes the app to
crash in some cases, when the file is not present on the device's
internal storage (for example, on Proton Drive).

app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.kt

@@ -9,6 +9,7 @@ import android.text.Spanned
 import android.text.format.Formatter
 import android.text.style.StyleSpan
 import android.util.Log
+import androidx.core.database.getLongOrNull
 import app.grapheneos.pdfviewer.R
 import org.json.JSONException
 
@@ -102,8 +103,9 @@ class DocumentPropertiesLoader(
 
             val indexSize: Int = cursor.getColumnIndex(OpenableColumns.SIZE)
             if (indexSize >= 0) {
-                val fileSize: Long = cursor.getString(indexSize).toLong()
-                collections[DocumentProperty.FileSize] = Formatter.formatShortFileSize(context, fileSize)
+                val fileSize = cursor.getLongOrNull(indexSize)
+                collections[DocumentProperty.FileSize] =
+                    fileSize?.let { Formatter.formatFileSize(context, it) } ?: context.getString(R.string.unknown_file_size)
             }
         }
         return collections

app/src/main/res/values/strings.xml

@@ -44,4 +44,6 @@
     <string name="creator">Creator</string>
     <string name="pdf_version">PDF version</string>
     <string name="pages">Pages</string>
+
+    <string name="unknown_file_size">Unknown</string>
 </resources>