Make sure MultiChar::data() constructs a valid string

mData may ultimately not be a valid C-string (e.g. if it contains 4 significant characters) so it may not necessarily be converted into a valid std::string

components/compiler/scanner.hpp

@@ -165,7 +165,8 @@ namespace Compiler
 
         std::string data()
         {
-            return mData;
+            // NB: mLength is the number of the last element in the array
+            return std::string(mData, mLength + 1);
         }
 
     private: