Document how to install mod_ecaptcha in GHCR container, fix minor bug

mod_ecaptcha/README.md

@@ -12,6 +12,9 @@ This small module uses the
 erlang library to generate CAPTCHA images suitable for ejabberd's
 [CAPTCHA](https://docs.ejabberd.im/admin/configuration/basic/#captcha) feature.
 
+Installing this module in a containerized ejabberd requires
+some additional steps, please read below.
+
 
 Basic Configuration
 -------------------
@@ -103,3 +106,40 @@ modules:
     font: "hplhs-oldstyle"
 ```
 
+
+Install in Container
+--------------------
+
+There are some additional steps to install this module in a containerized ejabberd.
+
+For example, if using the container image available at GitHub Container Registry:
+```
+docker run --name ejabberd -it -p 5222:5222 -p 5280:5280 -p 5288:5288 ghcr.io/processone/ejabberd:23.01 live
+```
+
+Install the dependencies required to compile C code:
+```
+docker exec --user root ejabberd apk add git make g++ freetype-dev erlang-dev
+```
+
+It's a good idea to update specs and modules source code:
+```
+docker exec ejabberd ejabberdctl modules_update_specs
+```
+
+Install the module so it gets the Erlang dependencies,
+then compile that dependency C code, and finally recompile it:
+```
+docker exec ejabberd ejabberdctl module_install mod_ecaptcha
+docker exec ejabberd make -C .ejabberd-modules/sources/ejabberd-contrib/mod_ecaptcha/deps/ecaptcha/c_src
+docker exec ejabberd ejabberdctl module_upgrade mod_ecaptcha
+```
+
+If using the Docker Hub Container, `ejabberdctl` is in a different path,
+please use those commands instead:
+```
+docker exec ejabberd bin/ejabberdctl modules_update_specs
+docker exec ejabberd bin/ejabberdctl module_install mod_ecaptcha
+docker exec ejabberd make -C .ejabberd-modules/sources/ejabberd-contrib/mod_ecaptcha/deps/ecaptcha/c_src
+docker exec ejabberd bin/ejabberdctl module_upgrade mod_ecaptcha
+```

mod_ecaptcha/src/mod_ecaptcha.erl

@@ -83,7 +83,7 @@ create_image(_Key) ->
                    font => get_opt(font)}
                 ),
     case Response of
-        {Phrase, PNGImage} when is_binary(PNGImage) ->
+        {Phrase, PNGImage} when is_binary(Phrase) ->
             PNGBin = binary:list_to_bin([PNGImage]),
             {ok, <<"image/png">>, Phrase, PNGBin};
         {error, Reason} ->