Fix to main when running without a mode

src/main.f90

@@ -38,8 +38,8 @@ program main
     end if
 
     !Check to make sure a mode was called
-    if (end_mode_arg=0) then 
-        stop "Please run cacmb using an available mode"
+    if (end_mode_arg==0) then 
+        stop "Nothing to do, please run cacmb using an available mode"
     end if
     !Now we loop through all of the arguments and check for passed options or for a filename to be written out
     arg_pos = end_mode_arg