hide sponsor form link if it's undefined, fixes #10

also edit a few if conditions to use `!= nil`, ref #8

_data/conf.yml

@@ -163,8 +163,8 @@ call-for-sponsors: true
 homepage-sponsor-button: true
 sponsorpage-sponsor-button: false
 # URL to document
-prospectus-document: ''
-sponsor-btn-link: 'https://na.eventscloud.com/sponsor.c4l21'
+# prospectus-document: ''
+# sponsor-btn-link: 'https://na.eventscloud.com/sponsor.c4l21'
 
 ##########
 # !!!NOTE!!! All 'end-date' vars should be in the following format: YYYY-MM-DD

prospectus/index.html

@@ -64,13 +64,18 @@ <h2>Impact of Support</h2>
  Your sponsorship of the conference can also provide immediate, concrete benefits to you and your organization. Code4Lib attendees include active practitioners who may be interested in your product, open source project, or services as well as department heads and senior administrators (approximately 17% of attendees last year) who make purchase decisions. Sponsors are strongly encouraged to send their staff to the conference to take advantage of access to the people and ideas who make up the Code4Lib community.
  </p>
 
- {% if site.data.conf.sponsor-contact-email != "" %}
+ {% if site.data.conf.sponsor-contact-email != nil or site.data.conf.sponsor-btn-link != nil %}
  <p>
- If you're ready to make a pledge, please <a href="{{site.data.conf.sponsor-btn-link}}">visit our sponsor registration form</a>. If you have questions, please get in touch with <a href="mailto:{{site.data.conf.sponsor-contact-email}}">{{site.data.conf.sponsor-contact-email}}</a>.
+ {% if site.data.conf.sponsor-btn-link != nil %}
+ If you're ready to make a pledge, please <a href="{{site.data.conf.sponsor-btn-link}}">visit our sponsor registration form</a>.
+ {% endif %}
+ {% if site.data.conf.sponsor-contact-email != nil %}
+ If you have questions, please get in touch with <a href="mailto:{{site.data.conf.sponsor-contact-email}}">{{site.data.conf.sponsor-contact-email}}</a>.
+ {% endif %}
  </p>
  {% endif %}
 
- {% if site.data.conf.prospectus-document != '' %}
+ {% if site.data.conf.prospectus-document != nil %}
  <p>
  A <a href="{{ site.data.conf.prospectus-document }}" onclick="ga('send', 'event', 'PDF', 'Download', 'Prospectus');">one-page information sheet</a> (PDF) is available to assist with making a case to sponsor the Code4Lib Conference.
  </p>
@@ -255,7 +260,7 @@ <h3>Post-Conference Video Production</h3>
  </div>
 </section>
 
-{% if site.data.conf.sponsor-contact-email != "" %}
+{% if site.data.conf.sponsor-contact-email != nil %}
 <!-- this floats in a tab along the side of the page -->
 <div id="contact">
  <p class="contact-tab">CONTACT</p>