Fix non-matching defaults. (#5452) (#5454)

(cherry picked from commit f84a9bf932)

plugins/modules/cloud/pubnub/pubnub_blocks.py

@@ -36,6 +36,7 @@ options:
       same play)."
     required: false
     type: str
+    default: ''
   password:
     description:
       - Password which match to account to which specified C(email) belong.
@@ -43,6 +44,7 @@ options:
       same play)."
     required: false
     type: str
+    default: ''
   cache:
     description: >
        In case if single play use blocks management module few times it is
@@ -57,7 +59,7 @@ options:
       manage blocks."
       - "User's account will be used if value not set or empty."
     type: str
-    required: false
+    default: ''
   application:
     description:
       - "Name of target PubNub application for which blocks configuration on