@whitts no... the title doesn't get injected. the code just takes the value of the title attribute from the <img> tag and displays it as a tool tip. you need to add the title attribute to the <img> tag with a value.
The weirdness is in fact the error comes randomly O_o
Steps to reproduce: continue pressing a "Page Reload Button" (Ctrl + R?), one per 10-20 attempts you'll catch the error. No matter what page you are on, even ACP.