[processing] fix TauDEM descriptions parsing

Author: alexbruy

python/plugins/processing/algs/taudem/TauDEMAlgorithm.py

@@ -112,7 +112,7 @@ def processAlgorithm(self, progress):
                 commands.append(param.name)
                 commands.append(param.value)
             elif isinstance(param, ParameterBoolean):
-                if not param.value:
+                if param.value:
                     commands.append(param.name)
             elif isinstance(param, ParameterString):
                 commands.append(param.name)