resolving issue with empty filter parameters

web/app/book.py

     books_query = Resource.query.filter_by(type=resource_type)
     for key in request.args.keys():
         if key != 'view':
-            if key == 'practice':
+            if (key == 'practice' and request.args.get(key) != ''):
                 books_1 = books_query.join(Relationship, Relationship.first_resource_id == Resource.id, isouter=True).filter(Relationship.second_resource_id==request.args.get(key))
                 books_2 = books_query.join(Relationship, Relationship.second_resource_id == Resource.id, isouter=True).filter(Relationship.first_resource_id==request.args.get(key))
                 books_query = books_1.union(books_2)
-            if key != 'practice':
+            if (key != 'practice' and request.args.get(key) != ''):
                 kwargs = {key: request.args.get(key)}
                 books_query = books_query.filter_by(**kwargs)
     # finalise the query

web/app/templates/resources.html

         {{ view_switch() }}
       
         {% if practices_filter%}
-        {{ filter_dropdown('practice', practices_filter, 'Practices') }}
+          {{ filter_dropdown('practice', practices_filter, 'Practices') }}
         {% endif %}
         {% if year_filter %}
-        {{ filter_dropdown_nokey('year', year_filter, 'Year') }}
+          {{ filter_dropdown_nokey('year', year_filter, 'Year') }}
         {% endif %}
         {% if typology_filter %}
-        {{ filter_dropdown_nokey('typology', typology_filter, 'Typologies') }}
+          {{ filter_dropdown_nokey('typology', typology_filter, 'Typologies') }}
         {% endif %}
         {% if languages_filter %}
-        {{ filter_dropdown_nokey('scriptingLanguage', languages_filter, 'Scripting languages') }}
+          {{ filter_dropdown_nokey('scriptingLanguage', languages_filter, 'Scripting languages') }}
         {% endif %}
         {% if licenses_filter %}
-        {{ filter_dropdown_nokey('license', licenses_filter, 'Licenses') }}
+          {{ filter_dropdown_nokey('license', licenses_filter, 'Licenses') }}
         {% endif %}
         {% if status_filter %}
-        {{ filter_dropdown_nokey('status', status_filter, 'Maintenance status') }}
+          {{ filter_dropdown_nokey('status', status_filter, 'Maintenance status') }}
         {% endif %}
       
         <a href="{{ request.base_url }}?view={{ view }}">Reset</a>
       
       <div>
         {% if view == 'list' %}
-        {% for resource in resources %}
-        {{ resource_list(resource, loop) }}
-        {% endfor %}
+          {% for resource in resources %}
+            {{ resource_list(resource, loop) }}
+          {% endfor %}
         {% else %}
-        {% for resource in resources %}
-        {{ resource_with_related(resource, loop) }}
-        {% endfor %}
+          {% for resource in resources %}
+            {{ resource_with_related(resource, loop) }}
+          {% endfor %}
         {% endif %}
       </div>
 

web/app/tool.py

     tools_query = Resource.query.filter_by(type=resource_type)
     for key in request.args.keys():
         if key != 'view':
-            if key == 'practice':
+            if (key == 'practice' and request.args.get(key) != ''):
                 tools_1 = tools_query.join(Relationship, Relationship.first_resource_id == Resource.id, isouter=True).filter(Relationship.second_resource_id==request.args.get(key))
                 tools_2 = tools_query.join(Relationship, Relationship.second_resource_id == Resource.id, isouter=True).filter(Relationship.first_resource_id==request.args.get(key))
                 tools_query = tools_1.union(tools_2)
-            if key == 'scriptingLanguage':
+            if (key == 'scriptingLanguage' and request.args.get(key) != ''):
                 regex = request.args.get(key) + "$|" + request.args.get(key) + "\s\/"
                 tools_query = tools_query.filter(Resource.scriptingLanguage.regexp_match(regex))
-            if key != 'practice' and key != 'scriptingLanguage':
+            if ((key != 'practice' and key != 'scriptingLanguage') and request.args.get(key) != ''):
                 kwargs = {key: request.args.get(key)}
                 tools_query = tools_query.filter_by(**kwargs)
     # finalise the query