Invalid JSON breaks custom query builder

[michael@…]

I just upgraded from 0.11.6 to 0.12.4 (and now 0.12.5dev-r11368) and am now getting a javascript syntax error on the custom query page. The offending javascript is the following:

var modes={"id":[{"name":"is","value":},{"name":"is not","value":"!"}],"select":[{"name":"is","value":},{"name":"is not","value":"!"}],"text":[{"name":"contains","value":"~"},{"name":"doesn't contain","value":"!~"},{"name":"begins with","value":"^"},{"name":"ends with","value":"$"},{"name":"is","value":},{"name":"is not","value":"!"}],"textarea":[{"name":"contains","value":"~"},{"name":"doesn't contain","value":"!~"}]};

To be sure, I check the generated JSON on the Demo site running Trac 0.12.5dev-r11311. Sure enough, that JSON is valid:

var modes={"id":[{"name":"is","value":""},{"name":"is not","value":"!"}],"select":[{"name":"is","value":""},{"name":"is not","value":"!"}],"text":[{"name":"contains","value":"~"},{"name":"doesn't contain","value":"!~"},{"name":"begins with","value":"^"},{"name":"ends with","value":"$"},{"name":"is","value":""},{"name":"is not","value":"!"}],"textarea":[{"name":"contains","value":"~"},{"name":"doesn't contain","value":"!~"}]};

I wonder if this bug is related to the version of python (2.4.3) I am running, and is similar in scope to #10771.