[gexiv2] Fix gtk-doc nullptr annotations - replace with NULL

[Jens Georg <jensgeorg src gnome org>]

commit 9e707d5a3418c7e9b8f5119941918b35f4b6541d
Author: postscript-dev <43813-postscript-dev users noreply gitlab gnome org>
Date:   Sat Feb 20 22:54:02 2021 +0000

    Fix gtk-doc nullptr annotations - replace with NULL

 gexiv2/gexiv2-metadata.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gexiv2/gexiv2-metadata.h b/gexiv2/gexiv2-metadata.h
index 806a271..6056cf4 100644
--- a/gexiv2/gexiv2-metadata.h
+++ b/gexiv2/gexiv2-metadata.h
@@ -672,7 +672,7 @@ gboolean            gexiv2_metadata_set_tag_string          (GExiv2Metadata *self, const 
gchar* ta
  * @self: An instance of #GExiv2Metadata
  * @tag: Exiv2 tag name
  * @type: The GExiv2StructureType specifying the type of structure
- * @error: (allow-none): A return location for a #GError or %nullptr
+ * @error: (allow-none): A return location for a #GError or %NULL
  *
  * The Exiv2 Tag Reference can be found at <ulink url="http://exiv2.org/metadata.html";></ulink>
  *
@@ -701,7 +701,7 @@ gboolean gexiv2_metadata_set_xmp_tag_struct (GExiv2Metadata *self, const gchar*
  * gexiv2_metadata_try_get_tag_interpreted_string:
  * @self: An instance of #GExiv2Metadata
  * @tag: Exiv2 tag name
- * @error: (allow-none): A return location for a #GError or %nullptr
+ * @error: (allow-none): A return location for a #GError or %NULL
  *
  * An interpreted string is one fit for user display.  It may display units or use formatting
  * appropriate to the type of data the tag holds.
@@ -735,7 +735,7 @@ gchar*                      gexiv2_metadata_get_tag_interpreted_string (GExiv2Metadata 
*self, const
  * gexiv2_metadata_try_get_tag_long:
  * @self: An instance of #GExiv2Metadata
  * @tag: Exiv2 tag name
- * @error: (allow-none): A return location for a #GError or %nullptr
+ * @error: (allow-none): A return location for a #GError or %NULL
  *
  * The Exiv2 Tag Reference can be found at <ulink url="http://exiv2.org/metadata.html";></ulink>
  *
@@ -764,7 +764,7 @@ glong                       gexiv2_metadata_get_tag_long            (GExiv2Metadata 
*self, const gchar* tag);
  * @self: An instance of #GExiv2Metadata
  * @tag: Exiv2 tag name
  * @value: The value to set or replace the existing value
- * @error: (allow-none): A return location for a #GError or %nullptr
+ * @error: (allow-none): A return location for a #GError or %NULL
  *
  * The Exiv2 Tag Reference can be found at <ulink url="http://exiv2.org/metadata.html";></ulink>
  *