templatetags: make |get return None on errors (#46507)

tests/test_templates.py

@@ -623,6 +623,11 @@ def test_get_filter():
     tmpl = Template('{{ foo|get:0 }}')
     assert tmpl.render({'foo': ['bar', 'baz']}) == 'bar'
 
+    tmpl = Template('{{ foo|get:0|default_if_none:"" }}')
+    assert tmpl.render({'foo': ""}) == ''
+    assert tmpl.render({'foo': None}) == ''
+    assert tmpl.render({'foo': 23}) == ''
+
 
 def test_get_on_lazy_var():
     FormDef.wipe()

wcs/qommon/templatetags/qommon.py

@@ -60,7 +60,10 @@ def get(mapping, key):
             key = int(key)
         except (TypeError, ValueError):
             pass
-    return mapping[key]
+    try:
+        return mapping[key]
+    except (TypeError, IndexError, KeyError):
+        return None
 
 
 @register.filter