When "entity type" : "all bundles" is selected, an empty list is returned.
This was caused because the target_bundles array was filled even if all bundles was selected.
Because of that, an entityCondition('bundle') was added to the entityFieldQuery() object.
As a consequence, an empty result was returned.
Corrected by adding a condition to check if bundle isn't empty.
Thanks for your report. Merged a slightly different fix in b5c6e31.
Automatically closed -- issue fixed for 2 weeks with no activity.
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