Don't validate on missing public key.

lib/pleroma/web/http_signatures/http_signatures.ex

@@ -47,6 +47,7 @@ defmodule Pleroma.Web.HTTPSignatures do
     else
       e ->
         Logger.debug("Could not public key!")
+        false
     end
   end
 

test/support/httpoison_mock.ex

@@ -401,6 +401,13 @@ defmodule HTTPoisonMock do
     }}
   end
 
+  def get("https://mst3k.interlinked.me/users/luciferMysticus", ["Accept": "application/activity+json"], _) do
+    {:ok, %Response{
+      status_code: 200,
+      body: File.read!("test/fixtures/httpoison_mock/lucifermysticus.json")
+    }}
+  end
+
   def get("https://mstdn.io/users/mayuutann", ["Accept": "application/activity+json"], _) do
     {:ok, %Response{
       status_code: 200,

test/web/http_sigs/http_sig_test.exs

@@ -183,6 +183,7 @@ defmodule Pleroma.Web.HTTPSignaturesTest do
         {"(request-target)", "post /inbox"}
       ]
     }
+
     assert HTTPSignatures.validate_conn(conn)
   end
 end