ambience: use zip_longest to not cut the reply

edmond/plugins/ambience.py

@@ -15,6 +15,7 @@ Words are actually the requester's name but it could be extended.
 """
 
 import random
+from itertools import zip_longest
 
 from edmond.plugin import Plugin
 from edmond.utils import proc
@@ -87,4 +88,7 @@ class AmbiencePlugin(Plugin):
         return chunk[:index] + word + chunk[index:]
 
     def interleave_word(self, chunk, word):
-        return "".join(a + b for a, b in zip(chunk, word))
+        return "".join(
+            a + b
+            for a, b in zip_longest(chunk, word, fillvalue='')
+        )