MAINT: fix compile warning.
MAINT: fix compile warning.

rgommers/pywt,michelp/pywt,grlee77/pywt,michelp/pywt,eriol/pywt,eriol/pywt,grlee77/pywt,Dapid/pywt,kwohlfahrt/pywt,rgommers/pywt,Dapid/pywt,aaren/pywt,rgommers/pywt,aaren/pywt,PyWavelets/pywt,Dapid/pywt,kwohlfahrt/pywt,eriol/pywt,rgommers/pywt,kwohlfahrt/pywt,ThomasA/pywt,PyWavelets/pywt,michelp/pywt,ThomasA/pywt,aaren/pywt,ThomasA/pywt