[warning: operation on 'battery' may be undefined] while compiling papracode-PCBV6.ino

[capsulecorplab]

/home/kasm-user/papra-pcb-firmware/papracode-PCBV6/papracode-PCBV6.ino: In function 'void loop()':
/home/kasm-user/papra-pcb-firmware/papracode-PCBV6/papracode-PCBV6.ino:183:11: warning: operation on 'battery' may be undefined [-Wsequence-point]
   battery = battery = ( ( battery * ( numBatterySamples - 1 ) ) + analogRead(analogBatt) ) / numBatterySamples;
   ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~