make PATH.resolve return an error result on paths with '' portions

src/library_path.js

@@ -85,7 +85,7 @@ mergeInto(LibraryManager.library, {
         if (typeof path !== 'string') {
           throw new TypeError('Arguments to path.resolve must be strings');
         } else if (!path) {
-          continue;
+          return ''; // an invalid portion invalidates the whole thing
         }
         resolvedPath = path + '/' + resolvedPath;
         resolvedAbsolute = path.charAt(0) === '/';

tests/filesystem/output.txt

@@ -1,14 +1,3 @@
-
-  isRoot: false
-  exists: true
-  error: 0
-  path: /abc
-  name: abc
-  object.contents: ["123","456","deviceA","localLink","rootLink","relativeLink"]
-  parentExists: true
-  parentPath: /
-  parentObject.contents: ["tmp","dev","forbidden","abc","def"]
-
 /
   isRoot: true
   exists: true

tests/filesystem/src.js

@@ -31,7 +31,6 @@ function explore(path) {
 }
 
 FS.currentPath = '/abc';
-explore('');
 explore('/');
 explore('.');
 explore('..');