#1542 (ok 4.3) Better error reporting in Designer; can get stuck Processing
Using Designer, I can cause it to get stuck on "Processing Request" without returning the MySQL error message to the user. It should catch the MySQL message and display it instead of getting stuck on the Processing Request message.
I discovered this when I had referencing ID values that were not in the referenced table, but the problem exists for other failure modes as well (for instance, trying to create a relation where the proper columns are not indexed).
The easiest way to reproduce my use case is to look at the attached .sql -- basically, main references an id 0 in reference which doesn't exist; this causes a problem creating the relation, but phpMyAdmin stops as "Processing Request" and doesn't do anything more. In my example data, EMPTYing the two tables allows one to create the relation, confirming that the problem is the improper id values.
Implemented with https://github.com/phpmyadmin/phpmyadmin/commit/8a410119cda3f7340f4953bb31f7a93d66cb536e