Check if disable-vec is given with the chemistry

configure.ac

@@ -1799,8 +1799,10 @@ esac
 
 if test "$with_chemistry" != "none"; then
    if test "$enable_hand_vec" == "yes"; then
-      if test "$with_hydro" == "gadget2"; then
-      AC_MSG_ERROR([Cannot run with hand vectorisation and chemistry yet. Please use --disable-hand-vec])
+      if test "$enable_vec" == "yes"; then
+         if test "$with_hydro" == "gadget2"; then
+            AC_MSG_ERROR([Cannot run with hand vectorisation and chemistry yet. Please use --disable-hand-vec])
+         fi
       fi
    fi
 fi