add "const" to PIByteArray::dataAs

libs/main/types/pibytearray.h

@@ -493,8 +493,8 @@ public:
 	inline const uchar * data(size_t index = 0) const { return d.data(index); }
 
 	template<typename T>
-	inline T dataAs(size_t index = 0) {
-		return *(T *)d.data(index);
+	inline T dataAs(size_t index = 0) const {
+		return *(const T *)d.data(index);
 	}
 
 	//! \~english Clear array, remove all elements.