[bugfix] Do not show empty error messages

Bug: T203462
Change-Id: I161c11194fd6287fee205c0fa03a8b1a5d7096cb
---
M pywikibot/bot.py
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/pywikibot/bot.py b/pywikibot/bot.py
index d450a6d..e9900eb 100644
--- a/pywikibot/bot.py
+++ b/pywikibot/bot.py
@@ -1084,9 +1084,10 @@
     if unknown_parameters:
         additional_text = 'Unknown parameter(s) "{0}"\n'.format(
             '", "'.join(unknown_parameters)) + additional_text
-    if not additional_text.endswith('\n'):
-        additional_text += '\n'
-    error(additional_text + 'Use -help for further information.')
+    if additional_text:
+        if not additional_text.endswith('\n'):
+            additional_text += '\n'
+        error(additional_text + 'Use -help for further information.')
 
 
 def writeToCommandLogFile():

