Add event meta filter to organizer page

src/pretix/base/models/event.py

@@ -667,7 +667,7 @@ class EventMetaProperty(LoggedModel):
     name = models.CharField(
         max_length=50, db_index=True,
         help_text=_(
-            "Can not contain spaces or special characters execpt underscores"
+            "Can not contain spaces or special characters except underscores"
         ),
         validators=[
             RegexValidator(

src/pretix/base/templatetags/urlreplace.py

@@ -4,7 +4,17 @@ register = template.Library()
 
 
 @register.simple_tag
-def url_replace(request, field, value):
+def url_replace(request, *pairs):
     dict_ = request.GET.copy()
-    dict_[field] = value
-    return dict_.urlencode()
+    key = None
+    for p in pairs:
+        if key is None:
+            key = p
+        else:
+            if p == "":
+                if key in dict_:
+                    del dict_[key]
+            else:
+                dict_[key] = p
+            key = None
+    return dict_.urlencode(safe='[]')