Add null check to response header method

[jordanpadams]

🗒️ Summary

Fix issues with nullpointerexception

⚙️ Test Data and/or Report

• Load any documents into your registry.
• Run curl command

$ curl --GET http://localhost:8080/search-ui-legacy/search?q=*:*


<div xmlns:html="http://www.w3.org/1999/xhtml" id="sidebar">
   <div class="sidebarSection">
      <h2>Refine Your Search</h2>
      <h3>
         <span class="pds_value">Type</span>
      </h3>
      <ul>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_type%3A%221%2Ccollection%22&amp;f.facet_type.facet.prefix=2%2Ccollection%2C">collection</a> (3661)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_type%3A%221%2Cbundle%22&amp;f.facet_type.facet.prefix=2%2Cbundle%2C">bundle</a> (557)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_type%3A%221%2Cdocument%22&amp;f.facet_type.facet.prefix=2%2Cdocument%2C">document</a> (45)</li>
      </ul>
      <h3>
         <span class="pds_value">Target</span>
      </h3>
      <ul>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Cplanet%22&amp;f.facet_target.facet.prefix=2%2Cplanet%2C">planet</a> (1581)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Csatellite%22&amp;f.facet_target.facet.prefix=2%2Csatellite%2C">satellite</a> (460)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Cother%22&amp;f.facet_target.facet.prefix=2%2Cother%2C">other</a> (262)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Ccalibration%22&amp;f.facet_target.facet.prefix=2%2Ccalibration%2C">calibration</a> (65)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Cring%22&amp;f.facet_target.facet.prefix=2%2Cring%2C">ring</a> (57)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Casteroid%22&amp;f.facet_target.facet.prefix=2%2Casteroid%2C">asteroid</a> (48)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Ccomet%22&amp;f.facet_target.facet.prefix=2%2Ccomet%2C">comet</a> (3)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Cmeteorite%22&amp;f.facet_target.facet.prefix=2%2Cmeteorite%2C">meteorite</a> (3)</li>
         <li>
            <a class="pds_value"
               href="?q=%2A%3A%2A&amp;fq=facet_target%3A%221%2Ctrans-neptunian%20object%22&amp;f.facet_target.facet.prefix=2%2Ctrans-neptunian%20object%2C">trans-neptunian object</a> (3)</li>
      </ul>
      <h3>
         <span class="pds_value">Investigation</span>
...

♻️ Related Issues

Resolves #7

Note: I know Exception e is very very bad for exception handling, but leaving for now.

[nutjob4life]

Looks safe!