Handle malformed browse parameters

Examples:

* https://art.wikidata.link/browse?P1433%27[0]=Q28861951
* https://art.wikidata.link/browse?P1433=Q28861951%27[0]

app.py

@@ -25,6 +25,7 @@ import json
 import os
 import locale
 import socket
+import re
 
 locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
 user_agent = 'Mozilla/5.0 (X11; Linux i586; rv:32.0) Gecko/20160101 Firefox/32.0'
@@ -77,6 +78,9 @@ isa_list = [
     'Q46686'      # reredos
 ]
 
+re_qid = re.compile(r'^Q(\d+)')
+re_pid = re.compile(r'^P(\d+)')
+
 @app.teardown_appcontext
 def shutdown_session(exception=None):
     database.session.remove()
@@ -524,10 +528,14 @@ def get_labels_db(keys):
     labels = {}
     missing = set()
     for qid in keys:
-        item = Item.query.get(qid[1:])
+        m = re_qid.match(qid)
+        if m:
+            item_id = int(m.group(1))
+            item = Item.query.get(item_id)
             if item:
                 labels[qid] = item.label
-        else:
+                continue
+
         missing.add(qid)
 
     page_size = 50
@@ -708,8 +716,20 @@ def get_facets(params):
     }
 
 def get_artwork_params():
-    return [(pid, qid) for pid, qid in request.args.items()
-            if pid.startswith('P') and qid.startswith('Q')]
+    params = []
+    for pid, qid in request.args.items():
+        m = re_pid.match(pid)
+
+        if not m:
+            continue
+        pid = m.group(0)
+
+        m = re_qid.match(qid)
+        if not m:
+            continue
+        qid = m.group(0)
+        params.append((pid, qid))
+    return params
 
 def filter_artwork(params):
     return wdqs.run_from_template_with_cache('query/find_more.sparql',