Add safety check for start dates unbound

cms/templates/edit_subsection.html

@@ -37,13 +37,13 @@
           <div class="field field-start-date">
             <label for="start_date">Release Day</label>
             <input type="text" id="start_date" name="start_date" 
-                value="${subsection.lms.start.strftime('%m/%d/%Y')}" 
+                value="${subsection.lms.start.strftime('%m/%d/%Y') if subsection.lms.start else ''}" 
                 placeholder="MM/DD/YYYY" class="date" size='15' autocomplete="off"/>
           </div>
           <div class="field field-start-time">
             <label for="start_time">Release Time (<abbr title="Coordinated Universal Time">UTC</abbr>)</label>
             <input type="text" id="start_time" name="start_time" 
-                value="${subsection.lms.start.strftime('%H:%M')}" 
+                value="${subsection.lms.start.strftime('%H:%M') if subsection.lms.start else ''}" 
                 placeholder="HH:MM" class="time" size='10' autocomplete="off"/>
           </div>
         </div>

cms/templates/overview.html

@@ -154,8 +154,12 @@
               <h3 class="section-name" data-name="${section.display_name_with_default | h}"></h3>
               <div class="section-published-date">
                 <%
-                  start_date_str = section.lms.start.strftime('%m/%d/%Y')
-                  start_time_str = section.lms.start.strftime('%H:%M')
+                  if section.lms.start is not None:
+                      start_date_str = section.lms.start.strftime('%m/%d/%Y')
+                      start_time_str = section.lms.start.strftime('%H:%M')
+                  else:
+                      start_date_str = ''
+                      start_time_str = ''
                 %>
                 %if section.lms.start is None:
                   <span class="published-status">This section has not been released.</span>