patch to set to NULL version column in coord_system table instead of blank

sql/patch_54_55_f.sql

+# patch_54_55_f.sql
+#
+# title: Set to NULL version column in coord_system table instead of blank.
+#
+# description:
+# The version column in the coord_system table has to be NULL when there
+# is no version for the coordinate system (at the moment, some had blank entries)
+
+UPDATE coord_system SET version = NULL WHERE version = '';
+
+# patch identifier
+INSERT INTO meta (species_id, meta_key, meta_value)
+VALUES (NULL, 'patch', 'patch_54_55_f.sql|coord_system.version_null');