Add checks for a nominalPower having a value and get slotIndex check correct

Author: PeterC1965

src/app/clusters/device-energy-management-server/device-energy-management-server.cpp

@@ -676,7 +676,7 @@ void Instance::HandleModifyForecastRequest(HandlerContext & ctx, const Commands:
         const Structs::SlotAdjustmentStruct::Type & slotAdjustment = iterator.GetValue();
 
         // Check for an invalid slotIndex
-        if (slotAdjustment.slotIndex > forecast.Value().slots.size())
+        if (slotAdjustment.slotIndex >= forecast.Value().slots.size())
         {
             ChipLogError(Zcl, "DEM: Bad slot index %d", slotAdjustment.slotIndex);
             ctx.mCommandHandler.AddStatus(ctx.mRequestPath, Status::Failure);
@@ -696,7 +696,8 @@ void Instance::HandleModifyForecastRequest(HandlerContext & ctx, const Commands:
         // NominalPower is only relevant if PFR is supported
         if (HasFeature(Feature::kPowerForecastReporting))
         {
-            if (!slot.minPowerAdjustment.HasValue() || !slot.maxPowerAdjustment.HasValue() ||
+            if (!slotAdjustment.nominalPower.HasValue() ||
+                !slot.minPowerAdjustment.HasValue() || !slot.maxPowerAdjustment.HasValue() ||
                 slotAdjustment.nominalPower.Value() < slot.minPowerAdjustment.Value() ||
                 slotAdjustment.nominalPower.Value() > slot.maxPowerAdjustment.Value())
             {