Debugger: Fix type issue in BList handler.

BListValueNode:
- BList's item count member is an int32. However, when the handler was reading
  said variable, it was mistakenly reading the number of bytes corresponding to
  to the address size of the architecture instead.This would cause the read to
  fail, and consequently BList and/or BObjectList variables to not display
  their contents properly on x86-64.

src/kits/debugger/value/value_nodes/BListValueNode.cpp

@@ -274,7 +274,7 @@ BListValueNode::ResolvedLocationAndValue(ValueLoader* valueLoader,
 			fItemCountLocation = memberLocation->PieceAt(0).address;
 
 			BVariant listSize;
-			error = valueLoader->LoadValue(memberLocation, valueType,
+			error = valueLoader->LoadValue(memberLocation, B_INT32_TYPE,
 				false, listSize);
 			if (error != B_OK)
 				return error;