Don't print error-message about missing impact

This fixes ticket:4573.

Belonging to [master]:
  - #2139

Author: sjoelund

Compiler/Script/CevalScriptBackend.mo

@@ -2132,7 +2132,7 @@ algorithm
         files = List.flatten(List.map(mps, System.moFiles));
         dirs = List.flatten(List.map(mps, getLibrarySubdirectories));
         files = List.map(List.map1(listAppend(files,dirs), System.strtok, ". "), listHead);
-        (str, status) = System.popen("impact search '' | perl -pe 's/\\e\\[?.*?[\\@-~]//g' | grep '[^ :]*:' | cut -d: -f1 2>&1");
+        (str, status) = System.popen("impact search '' 2>&1 | perl -pe 's/\\e\\[?.*?[\\@-~]//g' | grep '[^ :]*:' | cut -d: -f1 2>&1");
         if 0==status then
           files = listAppend(System.strtok(str,"\n"), files);
         end if;