@Override
			public boolean isEnabledForContext(ActionContext context) {
				return plugin.getCurrentProgram() != null;
			}
Apparently, we create fake function markup for external functions.  Thus, there is no
real function at that address and our plugin has to do some work to find out where
we 'hang' references to the external function, which is itself a Function.  These 
fake function will usually just be a pointer to another function.

@param function the function to resolve; if it is not null, then it will be used
@param address the address for which to find a function
@return either the given function if non-null, or a function being referenced from the
        given address.
Ghidra/Features/DecompilerDependent/src/main/java/ghidra/app/plugin/core/decompiler/taint/TaintPlugin.java