Rescue when member plugin's publication_date is nil

vendor/built_in_modules/personal_book/app/models/writing_book.rb

@@ -91,9 +91,10 @@ class WritingBook
     title << self.publisher if self.publisher.present?
     title << self.isbn if self.isbn.present?
 
-    pd = self.publish_date.strftime("%Y-%m-%d").split('-')
-
-    title << pd[0]+"/"+pd[1]
+    if !self.publish_date.nil?
+      pd = self.publish_date.strftime("%Y-%m-%d").split('-')
+      title << pd[0]+"/"+pd[1]
+    end
 
     # title << "(#{self.journal_level_types.collect{|x| x.title}.join(', ')})"
     title.join(', ') 

vendor/built_in_modules/personal_conference/app/models/writing_conference.rb

@@ -88,9 +88,11 @@ class WritingConference
 
     title << self.authors if self.authors.present?
 
-    pd = self.publication_date.strftime("%Y-%m-%d").split('-')
+    if !self.publication_date.nil?
+      pd = self.publication_date.strftime("%Y-%m-%d").split('-')
+      title << pd[0]
+    end
 
-    title << pd[0]
     title << self.paper_title if self.paper_title.present?
     title << self.conference_title if self.conference_title.present?
     title << self.location if self.location.present?

vendor/built_in_modules/personal_journal/app/models/writing_journal.rb

@@ -94,9 +94,10 @@ class WritingJournal
 
     title << self.authors if self.authors.present?
 
-    pd = self.publication_date.strftime("%Y-%m-%d").split('-')
-
-    title << pd[0]
+    if !self.publication_date.nil?
+      pd = self.publication_date.strftime("%Y-%m-%d").split('-')
+      title << pd[0]
+    end
     title << self.paper_title if self.paper_title.present?
     title << self.journal_title if self.journal_title.present?
     title << self.vol_no if (self.vol_no.present? && self.vol_no != "0")