add a null check at getting OTG files

build.gradle

@@ -6,7 +6,7 @@ buildscript {
         propMinSdkVersion = 16
         propTargetSdkVersion = propCompileSdkVersion
         propVersionCode = 1
-        propVersionName = '3.13.8'
+        propVersionName = '3.13.9'
         kotlin_version = '1.2.21'
         support_libs = '27.0.2'
     }

commons/src/main/kotlin/com/simplemobiletools/commons/extensions/Context-storage.kt

@@ -318,7 +318,10 @@ fun Context.getOTGItems(path: String, countHiddenItems: Boolean, getProperFileSi
             continue
         }
 
-        rootUri = rootUri.findFile(part)
+        val file = rootUri.findFile(part)
+        if (file != null) {
+            rootUri = file
+        }
     }
 
     val files = rootUri.listFiles()