QGIS » QGIS Application

In the "Add PostGIS Table(s)" dialog, when no layers are selected, the "Add" button is enabled. Clicking this button shows an information dialog:

You must select a table in order to add a layer.

Although this is all logical at a basic level, it could be confusing to the user. Particularly if they had already selected a layer, then double-clicked it to build a query, and the layer became unselected. The "Add" button should only be enabled when there are greater than zero layers selected, otherwise it should be disabled.

As a minor touch-up, the dialog does not list PostGIS "tables", rather they are layers (as the pop-up text shows for the icon). These can be any number of combinations of tables and/or views with one or more geometry/geography columns .. or simply put, layers.