changed error code if UrQMD fails to find collision

(cherry picked from commit 6991bd75)

modules/urqmd/urqmd.f

@@ -339,8 +339,8 @@ c~              stop
            endif
            if (noc.ge.50000) then
              print *,'UrQMD terminating...'
-             call exit(2) ! think of a better way to hand over the error
-                          ! to C++
+             call exit(333) ! think of a better way to hand over the error
+                            ! to C++
            endif
            goto 1
          endif