fix: og:image URL is incorrect (#1468)

Introduced by #1463

_includes/head.html

@@ -26,7 +26,7 @@
       {%- capture old_url -%}{{ src | absolute_url }}{%- endcapture -%}
       {%- capture new_url -%}{{ img_url }}{%- endcapture -%}
 
-      {% assign seo_tags = seo_tags | replace: old, new %}
+      {% assign seo_tags = seo_tags | replace: old_url, new_url %}
     {% endunless %}
 
   {% elsif site.social_preview_image %}

_includes/img-url.html

@@ -12,13 +12,21 @@
 {% assign url = include.src %}
 
 {%- if url -%}
-  {%- comment -%} CND URL {%- endcomment -%}
+  {% unless url contains ':' %}
-  {% assign prefix = site.img_cdn | default: '' | relative_url %}
+    {%- comment -%} CND URL {%- endcomment -%}
+    {% assign prefix = site.img_cdn | default: '' | relative_url %}
 
-  {%- comment -%} Add page image path prefix {%- endcomment -%}
+    {%- comment -%} Add page image path prefix {%- endcomment -%}
-  {% assign url = include.img_path | default: '' | append: '/' | append: url %}
+    {% assign url = include.img_path | default: '' | append: '/' | append: url %}
 
-  {% assign url = prefix | append: '/' | append: url | replace: '///', '/' | replace: '//', '/' | replace: ':', ':/' %}
+    {% assign url = prefix
+      | append: '/'
+      | append: url
+      | replace: '///', '/'
+      | replace: '//', '/'
+      | replace: ':', ':/'
+    %}
+  {% endunless %}
 {%- endif -%}
 
 {{- url -}}