logging: Guard against log color being undefined.

The 'info' log facility uses the default color, which is not present in
`LEVEL_COLORS`, thus `undefined` and unable to be `slice`d.

(As reported by @brucejo75).

Refs: https://github.com/meteor/meteor/pull/8728#issuecomment-336324674
Refs: meteor/meteor#9170

packages/logging/logging.js

@@ -55,7 +55,7 @@ var META_COLOR = 'blue';
 // ops per second (on Node 8) by caching "process.platform".
 var isWin32 = typeof process === 'object' && process.platform === 'win32';
 var platformColor = function (color) {
-  if (isWin32 && color.slice(-6) !== 'Bright') {
+  if (isWin32 && typeof color === 'string' && color.slice(-6) !== 'Bright') {
     return color + 'Bright';
   }
   return color;

packages/logging/package.js

@@ -1,6 +1,6 @@
 Package.describe({
   summary: "Logging facility.",
-  version: '1.1.18'
+  version: '1.1.19'
 });
 
 Npm.depends({