fix argument check for assimp cmdline tool

`assimp cmpdump` expects two files as arguments.
so we need to check for at least 2 extra arguments (rather than only check
for !<1 and access both)

tools/assimp_cmd/CompareDump.cpp

@@ -881,7 +881,7 @@ int Assimp_CompareDump (const char* const* params, unsigned int num)
     }
 
     // assimp cmpdump actual expected
-    if (num < 1) {
+    if (num < 2) {
         std::cout << "assimp cmpdump: Invalid number of arguments. "
             "See \'assimp cmpdump --help\'\r\n" << std::endl;
         return 1;