Updated the mimedetect and added a helper function to process dsids that are not in an objects content model, such as user added.

includes/datastream.version.inc

@@ -231,6 +231,34 @@ function islandora_revert_datastream_version_form_submit(array $form, array &$fo
   $form_state['redirect'] = "islandora/object/{$islandora_object->id}/datastream/{$datastream_to_revert->id}/version";
 }
 
+/**
+ * Process available dsids, mime and extensions for a given object.
+ *
+ * @param AbstractObject $object
+ *   The FedoraObject to process available extensions
+ *
+ * @return array()
+ *   An associative array, merged from calls to
+ *   islandora_get_datastreams_requirements_from_content_models()
+ *   and an objects dsid's.
+ */
+function islandora_get_object_extensions(AbstractObject $object) {
+  $extensions = islandora_get_datastreams_requirements_from_models($object->models);
+  foreach($object as $datastream){
+    // Could be a datastream not associated in a content model,
+    // such as user added.
+    if (!isset($extensions[$datastream->id])) {
+      // Add the extensions manually.
+      $extensions[$datastream->id] = array(
+        'id' => $datastream->id,
+        'optional' => TRUE,
+        'mime' => array($datastream->mimeType),
+      );
+    }
+  }
+  return $extensions;
+}
+
 /**
  * The admin replace datastream form.
  *
@@ -252,12 +280,15 @@ function islandora_datastream_version_replace_form($form, &$form_state, Abstract
   $form_state['object_id'] = $object->id;
   $form_state['dsid'] = $datastream->id;
   $form_state['object'] = $object;
-  $extensions = islandora_get_datastreams_requirements_from_models($object->models);
+  $extensions = islandora_get_object_extensions($object);
   $mime_detect = new MimeDetect();
   $ext = array();
-  foreach ($extensions[$datastream->id]['mime'] as $key => $value) {
+  if (isset($extensions[$datastream->id])) {
-    $str = $mime_detect->getExtension($value);
+    foreach ($extensions[$datastream->id]['mime'] as $key => $value) {
-    array_push($ext, $str);
+      dsm($value, "getting value for");
+      $str = $mime_detect->getExtension($value);
+      array_push($ext, $str);
+    }
   }
   $comma = count($ext) > 1 ? "," : "";
   $ext = array(implode($comma, $ext));

includes/mime_detect.inc

@@ -144,7 +144,7 @@ class MimeDetect {
     "ief" => "image/ief",
     "jpeg" => "image/jpeg",
     "jpe" => "image/jpeg",
-    "jpg" => "image/jpeg",
+    "jpg" => "image/jpg",
     "jp2" => "image/jp2",
     "png" => "image/png",
     "tiff" => "image/tiff",