Full title should be nil if they haven't specified a title

lib/stanford-mods/searchworks.rb

@@ -153,12 +153,13 @@ def title
         first_title_info_node.title.text.strip.empty?   ? nil : first_title_info_node.title.text.strip
       end
 
+      # Searchworks requires that the MODS has a '//titleInfo/title'
       # @return [String] value for title_245_search, title_full_display
       def sw_full_title
+        return nil if !first_title_info_node || !title
 
-        return nil unless first_title_info_node
         preSubTitle = nonSort_title ? [nonSort_title, title].compact.join(" ") : title
-        preSubTitle.sub!(/:$/, '') if preSubTitle # remove trailing colon
+        preSubTitle.sub!(/:$/, '')
 
         subTitle = first_title_info_node.subTitle.text.strip
         preParts = subTitle.empty? ? preSubTitle : preSubTitle + " : " + subTitle

spec/searchworks_title_spec.rb

@@ -27,6 +27,19 @@
     end
   end
 
+  context 'when titleInfo contains a subTitle but no title' do
+    let(:record) do
+      m = "<mods #{@ns_decl}><titleInfo><subTitle>An overview from 1942-1950</subTitle></titleInfo></mods>"
+      rec = Stanford::Mods::Record.new
+      rec.from_str m
+      rec
+    end
+
+    it 'returns nil' do
+      expect(record.sw_full_title).to be_nil
+    end
+  end
+
   context 'missing title node' do
     it 'deals with missing titleInfo node' do
       m = "<mods #{@ns_decl}></mods>"