Bugfix for #539.

OctoLinker stopped working, because the key decompress-response was defined with a boolean value instead of a string.

	"browser": {
		"decompress-response": false,
		"electron": false
	},

This was causing the following runtime error
TypeError: Cannot read property 'length' of undefined.

I fixed this issue in two places. First, the npm plugin returns early if the given value is not from type string. Second, if a capture group is empty (which should be never the case), the current node will be returned without adding a link.