[gnome-photos] image-view-helper: Be more strict about what is acceptable

[Debarshi Ray <debarshir src gnome org>]

commit 8e4881b17bac5051770436dd0b4e8f081bc813d9
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Jan 10 20:15:39 2018 +0100

    image-view-helper: Be more strict about what is acceptable

 src/photos-image-view-helper.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/photos-image-view-helper.c b/src/photos-image-view-helper.c
index 57439a9b..93be0218 100644
--- a/src/photos-image-view-helper.c
+++ b/src/photos-image-view-helper.c
@@ -127,6 +127,7 @@ void
 photos_image_view_helper_set_zoom (PhotosImageViewHelper *self, gdouble zoom)
 {
   g_return_if_fail (PHOTOS_IS_IMAGE_VIEW_HELPER (self));
+  g_return_if_fail (zoom > 0.0);
 
   if (photos_utils_equal_double (self->zoom, zoom))
     return;