Fix a couple of other missing getApplicationTransactionCommentObject() implementations

Summary:
See PHI165. See D18715. These objects (projects, blogs) also need implementations now.

(I thought about making this method `abstract` or doing try/catch to maybe make this more robust, but I think this should be the end of it, and those changes have mild complexity/compatibility/risk issues.)

Test Plan: Changed `bin/search index` to index only one document of each type, ran `bin/search index --all --force`, saw no more comment-related errors.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18729

src/applications/phame/storage/PhameBlogTransaction.php

@@ -15,6 +15,10 @@ final class PhameBlogTransaction
     return PhabricatorPhameBlogPHIDType::TYPECONST;
   }
 
+  public function getApplicationTransactionCommentObject() {
+    return null;
+  }
+
   public function getBaseTransactionClass() {
     return 'PhameBlogTransactionType';
   }

src/applications/project/storage/PhabricatorProjectTransaction.php

@@ -19,6 +19,10 @@ final class PhabricatorProjectTransaction
     return PhabricatorProjectProjectPHIDType::TYPECONST;
   }
 
+  public function getApplicationTransactionCommentObject() {
+    return null;
+  }
+
   public function getBaseTransactionClass() {
     return 'PhabricatorProjectTransactionType';
   }