aws: really unset AWS*PROFILE variables in asp function (#7838)

plugins/aws/aws.plugin.zsh

@@ -5,13 +5,15 @@ function agp {
 }
 
 function asp {
-  export AWS_DEFAULT_PROFILE=$1
-  export AWS_PROFILE=$1
-  export AWS_EB_PROFILE=$1
-
   if [[ -z "$1" ]]; then
+    unset AWS_DEFAULT_PROFILE AWS_PROFILE AWS_EB_PROFILE
     echo AWS profile cleared.
+    return
   fi
+
+  export AWS_DEFAULT_PROFILE=$1
+  export AWS_PROFILE=$1
+  export AWS_EB_PROFILE=$1
 }
 
 function aws_change_access_key {