Godot version: 3.2.2
OS/device including version:
Issue description:
If i press the highlighted [leer] (which means "empty"), I chose "New Image" on the dropdown-menu, and these errors appear in the output-tab:
GLES2: drivers/gles2/rasterizer_storage_gles2.cpp:810 - Condition "texture->data_size == 0 && !texture->render_target" is true. Returned: Ref
GLES3: drivers/gles3/rasterizer_storage_gles3.cpp:1101 - Condition "texture->data_size == 0 && !texture->render_target" is true. Returned: Ref
This happens both in GLES2 and GLES3-Mode. Seems to be a driver issue.
Steps to reproduce:
Open a new project, in the Scene tab, add a Control-Node and add a TextureButton as a child of Control-Node. In the Inspector-tab, choose the "Textures"-dropdown menu, choose "Normal", and add a "New Image-Texture". Then, you can see a option called "Image", which is empty. If pressed, you can choose to add a image by pressing "New Image".
Minimal reproduction project:
you can just drag and drop an image file on it.

is there a particular reason to do those many steps?
As suggested by @volzhs the proper workflow is to assign an existing image file, either by drag & drop, or by selecting "Load" instead of "New ImageTexture" in the dropdown menu.
The current ux is not really beginner-friendly though so here's a possible improvement:
It would be nice to message the user when assigning an empty texture or image (probably using configuration warning) instead of errors in the renderer.
@volzhs Oh god, I didn't really think of that. Thanks, this works now.
Most helpful comment
As suggested by @volzhs the proper workflow is to assign an existing image file, either by drag & drop, or by selecting "Load" instead of "New ImageTexture" in the dropdown menu.
The current ux is not really beginner-friendly though so here's a possible improvement:
It would be nice to message the user when assigning an empty texture or image (probably using configuration warning) instead of errors in the renderer.