pv4 doesn't return http method sometimes

Change-Id: I092024292f0434922f4ceef864364879d213d2dd
Reviewed-on: https://gerrit.instructure.com/69901
Reviewed-by: August Thornton <august@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <cody@instructure.com>

app/models/page_view/pv4_client.rb

@@ -50,7 +50,7 @@ class PageView
         pv['account_id'] = pv.delete('root_account_id')
         pv['remote_ip'] = pv.delete('client_ip')
         pv['render_time'] = pv.delete('microseconds').to_f / 1_000_000
-        pv['http_method'].downcase!
+        pv['http_method'].try(:downcase!)
 
         PageView.from_attributes(pv)
       end