refactor: remove !! operator from upload snippets

Author: thatfiredev

storage/app/src/main/java/com/google/firebase/referencecode/storage/kotlin/UploadActivity.kt

@@ -12,7 +12,7 @@ import com.google.firebase.storage.UploadTask
 abstract class UploadActivity : AppCompatActivity() {
 
     // storageRef was previously used to transfer data.
-    private var storageRef: StorageReference? = null
+    private lateinit var storageRef: StorageReference
     private var saved: Boolean = false
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -40,16 +40,16 @@ abstract class UploadActivity : AppCompatActivity() {
 
         // Find all UploadTasks under this StorageReference (in this example, there should be one)
 
-        storageRef?.activeUploadTasks?.let { it ->
-            if (it.size > 0) {
-                // Get the task monitoring the upload
-                val task = it[0]
+        val tasks = storageRef.activeUploadTasks
 
-                // Add new listeners to the task using an Activity scope
-                task.addOnSuccessListener(this) {
-                    // Success!
-                    // ...
-                }
+        if (tasks.size > 0) {
+            // Get the task monitoring the upload
+            val task = tasks[0]
+
+            // Add new listeners to the task using an Activity scope
+            task.addOnSuccessListener(this) {
+                // Success!
+                // ...
             }
         }
     }
@@ -61,7 +61,7 @@ abstract class UploadActivity : AppCompatActivity() {
         var uploadTask: UploadTask
 
         // [START save_before_restart]
-        uploadTask = storageRef!!.putFile(localFile)
+        uploadTask = storageRef.putFile(localFile)
         uploadTask.addOnProgressListener { taskSnapshot ->
             sessionUri = taskSnapshot.uploadSessionUri
             if (sessionUri != null && !saved) {
@@ -75,7 +75,7 @@ abstract class UploadActivity : AppCompatActivity() {
         // [START restore_after_restart]
         // resume the upload task from where it left off when the process died.
         // to do this, pass the sessionUri as the last parameter
-        uploadTask = storageRef!!.putFile(localFile,
+        uploadTask = storageRef.putFile(localFile,
                 StorageMetadata.Builder().build(), sessionUri)
         // [END restore_after_restart]
     }