Fix CONRAD.getClasses when running with pyconrad

[theHamsta]

On pyconrad, the thread that runs CONRAD GUI is not the first thread on the JVM.
Therefore or for some other reason, Thread.currentThread().getContextClassLoader() returns null.
We can solve this problem by patching a private member from pyconrad.

Any better ideas? Setting the setContextClassLoader on the pyconrad side did not work. Patching the whole getClasses method with pyconrad was to drastic for me.

[akmaier]

Did you check whether the StandAlone Version still works after this change? Do we need a new Conrad release then?

[theHamsta]

I only tested it with the compiled Java code. With and without pyconrad.

Since the patch only does things if classLoader == null, I don't fear any deteriorations. classLoadder != null is even a assertion in the next line of the original code and we only try to fix things if that condition is not fulfilled.

Finding all filter classes when launched by pyconrad would require this patch and a new CONRAD release.

[theHamsta]

JAR can be tested by

pip install pyconrad --upgrade
export CONRAD_DEV_DIRS=/folder/of/fixed/jar/file/
conrad

Expected result: Loading CONRAD filters in CONRAD GUI only works if CONRAD_DEV_DIRS is set.