Omar is mostly right.
Connecting a Color Output (of the Image Node) directly into a Shader Input used to be forbidden, but nowadays Blender inserts an Emission Shader Node in between (behind the scenes)…the problem you get, is when you have a black image, send to an Emission, that is like having no Emission at all…
I’d use a Mix Color Node and plug that into the Base Color of the Principled Shader, or use the Color Ouput of the Image Texture Nodes directly into the Base Color of the Principled.
Or use your setup, but insert another Principled Shader in between the Text and the Mix Shader.
