Removes error messages when getting repo status

When `get_git_status` fails the inner `os.execute` call print error
message to console. This removes all error messages fro such cases.

config/cmder.lua

@@ -136,7 +136,7 @@ end
  -- @return {bool}
 ---
 function get_git_status()
-    return os.execute("git diff --quiet --ignore-submodules HEAD")
+    return os.execute("git diff --quiet --ignore-submodules HEAD 2>nul")
 end
 
 function git_prompt_filter()