Probably empty and/or a tangle web of wires. Pull the radio, usually 4 screws, and take a peek.
I can't see what radio that is, but if you search the model number you can find the install paperwork to see where the screws are. Most have "dress" covers over the screws.
Mine has a nice little finished compartment above the radio, where there are a couple of coaxial connectors, the antenna booster, a 120VAC outlet, and a 12 vdc power supply. I believe it's a space designed for a DVD player.
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Bill
2011 Dodge Ram 1500 HEMI Quad Cab
2011 Jay Flight 26BH