Fixed KeyError when user provides no user-agent

VIPSWeb/views.py

@@ -31,7 +31,8 @@ def index(request):
     try:
         # Check if user is on stock Android browser, which performs poorly with OpenLayers
         user_is_stock_android = False
-        user_agent = request.META['HTTP_USER_AGENT']
+        user_agent = request.META.get('HTTP_USER_AGENT',"")
+        
         if user_agent.find("Android") >= 0 and user_agent.find("Windows") < 0:
             chrome_index = user_agent.find("Chrome")
             if  chrome_index < 0: