test: suppress compiler warning in test_bigint
Currently the are two of following compiler warnings is generated:
In file included from ../test_bigint.c:5:
../test_bigint.c: In function ‘CreateTooBigBigInt’:
../test_bigint.c:120:22: warning:
‘words’ may be used uninitialized [-Wmaybe-uninitialized]
This commit initialized the words array to avoid these warnings.