Add `_#toString` test for nullish values.
Add `_#toString` test for nullish values.

Xotic750/lodash,woldie/lodash,Droogans/lodash,Droogans/lodash,woldie/lodash,benweet/lodash,boneskull/lodash,tquetano-r7/lodash,steelsojka/lodash,tquetano-r7/lodash,msmorgan/lodash,beaugunderson/lodash,boneskull/lodash,benweet/lodash,zestia/lodash,benweet/lodash,steelsojka/lodash,tonyonodi/lodash,Xotic750/lodash,rlugojr/lodash,msmorgan/lodash,woldie/lodash,rlugojr/lodash,tonyonodi/lodash,tquetano-r7/lodash,Droogans/lodash,zestia/lodash,Xotic750/lodash,beaugunderson/lodash,mshoaibraja/lodash,mshoaibraja/lodash,mshoaibraja/lodash,zestia/lodash