closes https://github.com/assimp/assimp/issues/2210: use different enum value.

code/STEPFile.h

@@ -142,7 +142,7 @@ namespace STEP {
     struct TypeError : DeadlyImportError {
         enum {
             ENTITY_NOT_SPECIFIED = 0xffffffffffffffffLL,
-            ENTITY_NOT_SPECIFIED_32 = -1u
+            ENTITY_NOT_SPECIFIED_32 = 0x00000000ffffffff
         };
 
         TypeError (const std::string& s,uint64_t entity = ENTITY_NOT_SPECIFIED, uint64_t line = SyntaxError::LINE_NOT_SPECIFIED);