OpAmp with inputs connected together
It is as you suspect.  An unused op-amp with inputs improperly connected.

From How to Properly Configure Unused Operational Amplifiers


  Degradation Conditions
  
  Connecting the input pins together or to the supply rails can lead to device
  damage. If configured like this, the input stage can suffer permanent electrical overstress (EOS) damage, as shown




It references The Unused Op Amp—what to do?



From Application Design Guidelines for LM324/LM358 Devices


  7.1 Do Not Connect Inputs Directly to Ground
  For both used and unused amplifiers, the inputs must not be connected directly to ground or any other low impedance node. Always add some resistance to limit the current to less than 10 mA, regardless of any possible fault condition. All the input pins have a diode from the input to the device’s GND, or V–, pin. In
  dual supply applications, the GND pin will be negative. However, during power up, power down, or supply faults, the GND pin may become positive. If this occurs then a grounded input pin will have potentially damaging current flow due to the input diode. Even if the GND pin is also grounded, such as in single supply applications, there is a possibility that the input ground will be negative relative to the op amp’s internal ground node. Ground differences occur when there is poor layout or high current transients, ∆i/∆t. Adding 1-kΩ to 10-kΩ series resistors to the input pin is acceptable in most applications.
  
  7.2 Unused Amplifier Connections
  Occasionally applications will not need all the amplifiers in a dual or quad package. The unused op amp should be connected in a way that is safe for the unused amplifier and doesn’t affect the used amplifiers. The best connection method puts the op amp into the normal linear operation range and no inputs are connected directly to low impedance nodes. The output of the op amp is not a low impedance node. The output by itself cannot provide a harmful voltage and/or current to the input. Therefore, no series resistor is needed between the input and output pins.