Fix 500er when calling protocol handler with invalid URL

app/services/diaspora_link_service.rb

@@ -10,8 +10,10 @@ class DiasporaLinkService
   end
 
   def find_or_fetch_entity
+    if type && guid
       entity_finder.find || fetch_entity
     end
+  end
 
   private
 
@@ -38,8 +40,8 @@ class DiasporaLinkService
   def parse
     normalize
     match = DiasporaFederation::Federation::DiasporaUrlParser::DIASPORA_URL_REGEX.match(link)
-    @author = match[1]
-    @type = match[2]
-    @guid = match[3]
+    if match
+      @author, @type, @guid = match.captures
+    end
   end
 end

spec/services/diaspora_link_service_spec.rb

@@ -40,5 +40,17 @@ describe DiasporaLinkService do
         expect(service.find_or_fetch_entity).to be_nil
       end
     end
+
+    context "with invalid links" do
+      it "returns nil when the link is invalid" do
+        service = described_class.new("web+diaspora://something_invalid")
+        expect(service.find_or_fetch_entity).to be_nil
+      end
+
+      it "returns nil when the author is valid, but rest of the link is invalid" do
+        service = described_class.new("web+diaspora://#{alice.diaspora_handle}/foo/bar")
+        expect(service.find_or_fetch_entity).to be_nil
+      end
+    end
   end
 end