[gnome-photos] thumbnail-factory: Fix typo and silence -Wpointer-compare

[Debarshi Ray <debarshir src gnome org>]

commit bff99d4595a6d458c75fb5528eb0f75c4ff33bc6
Author: Timm Bäder <mail baedert org>
Date:   Tue Jun 6 18:54:21 2017 +0200

    thumbnail-factory: Fix typo and silence -Wpointer-compare
    
    Fallout from 48c353aee8b89fdc002dcfc40e14177fb7eab603

 src/photos-thumbnail-factory.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/photos-thumbnail-factory.c b/src/photos-thumbnail-factory.c
index 01f5dc5..229e41d 100644
--- a/src/photos-thumbnail-factory.c
+++ b/src/photos-thumbnail-factory.c
@@ -380,7 +380,7 @@ photos_thumbnail_factory_generate_thumbnail (PhotosThumbnailFactory *self,
   g_return_val_if_fail (PHOTOS_IS_THUMBNAIL_FACTORY (self), FALSE);
   g_return_val_if_fail (G_IS_FILE (file), FALSE);
   g_return_val_if_fail (g_file_is_native (file), FALSE);
-  g_return_val_if_fail (mime_type != NULL && mime_type != '\0', FALSE);
+  g_return_val_if_fail (mime_type != NULL && mime_type[0] != '\0', FALSE);
   g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), FALSE);
   g_return_val_if_fail (error == NULL || *error == NULL, FALSE);