Use unsigned types for Items array indexes consistently

Actual type used varied based on context, this addresses some type conversion warnings.

Source/items.cpp

@@ -40,15 +40,15 @@ namespace devilution {
 
 /** Contains the items on ground in the current game. */
 Item Items[MAXITEMS + 1];
-int ActiveItems[MAXITEMS];
-int ActiveItemCount;
+uint8_t ActiveItems[MAXITEMS];
+uint8_t ActiveItemCount;
 /**
  * @brief Contains indexes of empty spaces in Items.
  *
  * This array effectively duplicates ActiveItems due to differences in implementation to other fixed buffers.
  * Eventually this can be removed and Items can be treated the same as how Missiles are tracked
  */
-int AvailableItems[MAXITEMS];
+uint8_t AvailableItems[MAXITEMS];
 bool ShowUniqueItemInfoBox;
 CornerStoneStruct CornerStone;
 bool UniqueItemFlags[128];
@@ -2597,9 +2597,9 @@ void InitItems()
 		item._iPostDraw = false;
 	}
 
-	for (int i = 0; i < MAXITEMS; i++) {
+	for (uint8_t i = 0; i < MAXITEMS; i++) {
+		ActiveItems[i] = i;
 		AvailableItems[i] = i;
-		ActiveItems[i] = 0;
 	}
 
 	if (!setlevel) {

Source/items.h

@@ -414,9 +414,9 @@ struct CornerStoneStruct {
 struct Player;
 
 extern Item Items[MAXITEMS + 1];
-extern int ActiveItems[MAXITEMS];
-extern int ActiveItemCount;
-extern int AvailableItems[MAXITEMS];
+extern uint8_t ActiveItems[MAXITEMS];
+extern uint8_t ActiveItemCount;
+extern uint8_t AvailableItems[MAXITEMS];
 extern bool ShowUniqueItemInfoBox;
 extern CornerStoneStruct CornerStone;
 extern bool UniqueItemFlags[128];

Source/loadsave.cpp

@@ -900,7 +900,7 @@ std::unordered_map<uint8_t, uint8_t> LoadDroppedItems(LoadHelper &file)
 	}
 	file.Skip(MAXITEMS * 2 - static_cast<size_t>(ActiveItemCount)); // Skip loading the rest of ActiveItems and AvailableItems, the indices are initialised below based on the number of active items
 
-	for (int i = 0; i < MAXITEMS; i++) {
+	for (uint8_t i = 0; i < MAXITEMS; i++) {
 		if (i < ActiveItemCount)
 			LoadItem(file, Items[i]);
 
@@ -1512,13 +1512,13 @@ void SavePortal(SaveHelper *file, int i)
 std::unordered_map<uint8_t, uint8_t> SaveDroppedItems(SaveHelper &file)
 {
 	// Vanilla Diablo/Hellfire initialise the ActiveItems and AvailableItems arrays based on saved data, so write valid values for compatibility
-	for (int i = 0; i < MAXITEMS; i++)
-		file.WriteLE<int8_t>(i); // Strictly speaking everything from ActiveItemCount onwards is unused but no harm writing non-zero values here.
-	for (int i = 0; i < MAXITEMS; i++)
-		file.WriteLE<int8_t>((i + ActiveItemCount) % MAXITEMS);
+	for (uint8_t i = 0; i < MAXITEMS; i++)
+		file.WriteLE<uint8_t>(i); // Strictly speaking everything from ActiveItemCount onwards is unused but no harm writing non-zero values here.
+	for (uint8_t i = 0; i < MAXITEMS; i++)
+		file.WriteLE<uint8_t>((i + ActiveItemCount) % MAXITEMS);
 
 	std::unordered_map<uint8_t, uint8_t> itemIndexes = { { 0, 0 } };
-	for (int i = 0; i < ActiveItemCount; i++) {
+	for (uint8_t i = 0; i < ActiveItemCount; i++) {
 		itemIndexes[ActiveItems[i] + 1] = i + 1;
 		SaveItem(file, Items[ActiveItems[i]]);
 	}
@@ -1534,7 +1534,7 @@ void SaveDroppedItemLocations(SaveHelper &file, const std::unordered_map<uint8_t
 {
 	for (int j = 0; j < MAXDUNY; j++) {
 		for (int i = 0; i < MAXDUNX; i++) // NOLINT(modernize-loop-convert)
-			file.WriteLE<int8_t>(itemIndexes.at(dItem[i][j]));
+			file.WriteLE<uint8_t>(itemIndexes.at(dItem[i][j]));
 	}
 }