Exclude empty items from the array

They are empty if NODE_PATH is empty, and split() returns [''].

Author: gaearon

packages/jest-resolve/src/__tests__/resolve-test.js

@@ -46,6 +46,7 @@ describe('findNodeModule', () => {
     const nodePaths = process.env.NODE_PATH
       ? process.env.NODE_PATH
           .split(path.delimiter)
+          .filter(Boolean)
           .map(p => path.resolve(resolvedCwd, p))
       : null;
 

packages/jest-resolve/src/index.js

@@ -55,6 +55,7 @@ const resolvedCwd = fs.realpathSync(process.cwd());
 const nodePaths = process.env.NODE_PATH
   ? process.env.NODE_PATH
       .split(path.delimiter)
+      .filter(Boolean)
       // The resolver expects absolute paths.
       .map(p => path.resolve(resolvedCwd, p))
   : null;