Plugin registration

[Nicolas]

How to troubleshoot plugin loading?
After restarting of NodeBB, none of available plugins do not load anymore.

Also, Reload give such error in console:

18/4 18:32 [34370] - error: TypeError: Reduce of empty array with no initial value
    at Array.reduce (native)
    at async.waterfall.x (/Users/nicolas/Documents/Works/JavaScript/NodeBB/src/plugins.js:343:8)
    at fn (/Users/nicolas/Documents/Works/JavaScript/NodeBB/node_modules/async/lib/async.js:641:34)
    at Immediate._onImmediate (/Users/nicolas/Documents/Works/JavaScript/NodeBB/node_modules/async/lib/async.js:557:34)
    at processImmediate [as _immediateCallback] (timers.js:358:17)
TypeError: Reduce of empty array with no initial value
    at Array.reduce (native)
    at async.waterfall.x (/Users/nicolas/Documents/Works/JavaScript/NodeBB/src/plugins.js:343:8)
    at fn (/Users/nicolas/Documents/Works/JavaScript/NodeBB/node_modules/async/lib/async.js:641:34)
    at Immediate._onImmediate (/Users/nicolas/Documents/Works/JavaScript/NodeBB/node_modules/async/lib/async.js:557:34)
    at processImmediate [as _immediateCallback] (timers.js:358:17)

Branch: 0.6.x

[Nicolas]

Solved by just reloading everything - several times: Database, NodeBB

[baris]

That error is caused by the following bit of code in src/plugins.js

paths = paths.map(function(pluginLib) {
	var parent = path.dirname(pluginLib);
	return cached.filter(function(libPath) {
		return libPath.indexOf(parent) !== -1;
	});
}).reduce(function(prev, cur) {
	return prev.concat(cur);
});

If paths is an empty array calling reduce will throw that error. We should add better checks to detect that.