fix: energy window

src/libdramsys/DRAMSys/simulation/Dram.cpp

@@ -316,6 +316,7 @@ void Dram::powerWindow()
 
         currentEnergy = this->DRAMPower->getTotalEnergy(clkCycles);
         windowEnergy = currentEnergy - previousEnergy;
+        previousEnergy = currentEnergy;
 
         // During operation the energy should never be zero since the device is always consuming
         assert(!(windowEnergy < 1e-15));