Stacktrace when enabling debugging

[ptitdoc]

_componentValues can be NoValue in some situation, which makes debugging crash:

  File "pyasn1/type/univ.py", line 2738, in prettyPrintType
    for idx, componentType in enumerate(self.componentType.values() or self._componentValues):

I fixed the bug by changing this line:

pyasn1/pyasn1/type/univ.py

Line 2722 in db8f1a7

for idx, componentType in enumerate(self.componentType.values() or self._componentValues):

to:

        enum = self.componentType.values()
        if not enum and not isinstance(self._componentValues,base.NoValue):
            enum = self._componentValues
        for idx, componentType in enumerate(enum):