ntfy loaded topic count bugfix

[caronc]

Description:

Related issue (if applicable): n/a

All services should return 1 at the very least; never 0 when getting a count.

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@ntfy-len-bugfix

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  ntfy://host/topic

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.27%. Comparing base (26d8e45) to head (34725d4).
Report is 15 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1094      +/-   ##
==========================================
- Coverage   99.27%   99.27%   -0.01%     
==========================================
  Files         136      138       +2     
  Lines       17753    17954     +201     
  Branches     3623     3663      +40     
==========================================
+ Hits        17625    17824     +199     
- Misses        119      121       +2     
  Partials        9        9              

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