Background
I included an image with changeable size in a post written about two months ago.
How/Why does this work?
- In brief: View
/javascripts/svg-resize-bar.js
. - For details: click the hyperlink above.
Problem

When I browsed any pages except that post which contains the
changeable SVG image, the above TypeError
was thrown.
Solution
From the error message TypeError: bar is null
and the filename
svg-resize-bar.js
on the right, an ordinary user who knows how to
write if-else statements should be able to solve this in a few
seconds: surround the part bar.onchange = function () { ... }
by the
if-else statement if (bar != null ) { ... }
.