bugfix(ui): creator could have potentially no identifiers

The macro authors should handle the case where there are no identifiers for a
author. Therefore this check had to be added.

NOTE:
further removed the copyright noting Mojib Wali. we stick with TU Graz
further added a newline in the end of the file

invenio_theme_tugraz/templates/invenio_theme_tugraz/macros/authors.html

@@ -1,8 +1,7 @@
 {#
     Copyright (C) 2020 Zenodo
     Copyright (C) 2020 TUGRAZ
-    Copyright (C) 2020 mojib wali.
-  
+
     invenio-theme-tugraz is free software; you can redistribute it and/or
     modify it under the terms of the MIT License; see LICENSE file for more
     details.
@@ -12,7 +11,7 @@
 
 {%- for creators in authors_list %}
 
-{%- if creators.identifiers.orcid %}
+{%- if creators.identifiers and creators.identifiers.orcid %}
 <a href="{{creators.identifiers.orcid|pid_url('orcid')}}" target="_blank" ><img class="inline-orcid" src="{{ url_for('static', filename='extra/orcid.png')}}" /></a>
 {%- endif %}
 
@@ -28,4 +27,4 @@
 <h5>{{group.grouper}}(s)</h5>
 {{authors(group.list)}}
 {%- endfor %}
-{%- endmacro %}
+{%- endmacro %}