Allow the no_course_image to come from the current theme

Fixes #67

changelog.d/20240219_134558_misilot_issue_67.md

@@ -0,0 +1,13 @@
+
+<!--
+Create a changelog entry for every new user-facing change. Please respect the following instructions:
+- Indicate breaking changes by prepending an explosion 💥 character.
+- Prefix your changes with either [Bugfix], [Improvement], [Feature], [Security], [Deprecation].
+- You may optionally append "(by @<author>)" at the end of the line, where "<author>" is either one (just one)
+of your GitHub username, real name or affiliated organization. These affiliations will be displayed in
+the release notes for every release.
+-->
+
+<!-- - 💥[Feature] Foobarize the blorginator. This breaks plugins by renaming the `FOO_DO` filter to `BAR_DO`. (by @regisb) -->
+<!-- - [Improvement] This is a non-breaking change. Life is good. (by @billgates) -->
+- 💥[Improvement] Allow the no_course_image.png image to pull from the current theme, not specifically named indigo (by @misilot)

tutorindigo/templates/indigo/lms/templates/course.html

@@ -8,7 +8,7 @@
 <article class="course" id="${course.id}" role="region" aria-label="${course.display_name_with_default}">
     <header class="course-image">
       <div class="cover-image">
-        <img src="${course.course_image_url}" onerror="this.src='/static/indigo/images/no_course_image.png';" alt="${course.display_name_with_default} ${course.display_number_with_default}" />
+        <img src="${course.course_image_url}" onerror='this.src="${static.url('images/no_course_image.png')}";' alt="${course.display_name_with_default} ${course.display_number_with_default}" />
       </div>
     </header>
     <div class="course-info" aria-hidden="true">

tutorindigo/templates/indigo/lms/templates/discovery/course_card.underscore

@@ -1,7 +1,7 @@
 <article class="course" role="region" aria-label="<%- content.display_name %>">
         <header class="course-image">
             <div class="cover-image">
-                <img src="<%- image_url %>" onerror="this.src='/static/indigo/images/no_course_image.png';" alt="<%- content.display_name %> <%- content.number %>" />
+                <img src="<%- image_url %>" onerror="this.src='${static.url('images/no_course_image.png')};" alt="<%- content.display_name %> <%- content.number %>" />
             </div>
         </header>
         <section class="course-info" aria-hidden="true">