YUIDoc can crash when @extends tag is empty

[roipoussiere]

When building the documentation from a folder containing only this js file:

/**
 * @class The foo class aims to crash YUIDoc.
 * @extends 
 */
function foo() {return 'bar';}

YUIDoc crashs with this stacktrace:

info: Starting YUIDoc@0.10.2 using YUI@3.18.1 with NodeJS@4.4.7
info: Scanning for yuidoc.json file.
info: Starting YUIDoc with the following options:
info: {"port":3000,"nocode":false,"paths":["."],"outdir":"./out"}
info: YUIDoc Starting from: .
warn: Found out dir, deleting: ./out
info: Making out dir: ./out
info: Parsed 8 files in 0.031 seconds
info: Building..
info: Compiling Templates
info: Making default directories: classes,elements,modules,files
info: Copying Assets
info: Rendering and writing 0 modules pages.
info: Finished writing module files
info: Rendering and writing 1 class pages.
info: Loading theme from /usr/lib/node_modules/yuidocjs/themes/default/theme.json
error: --------------------------------------------------------------------------
error: An uncaught YUIDoc error has occurred, stack trace given below
error: --------------------------------------------------------------------------
error: TypeError: item.indexOf is not a function
    at Object.<anonymous> (/usr/lib/node_modules/yuidocjs/lib/builder.js:75:22)
    at Object.eval (eval at <anonymous> (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-compiler/handlebars-compiler-min.js:11:641), <anonymous>:4:82)
    at Object.s [as fn] (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-base/handlebars-base-min.js:7:707)
    at Object.<anonymous> (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-base/handlebars-base-min.js:6:2855)
    at Object.eval (eval at <anonymous> (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-compiler/handlebars-compiler-min.js:11:641), <anonymous>:9:26)
    at Object.o (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-base/handlebars-base-min.js:7:310)
    at Object.o [as classes] (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-compiler/handlebars-compiler-min.js:9:5480)
    at Object.i [as invokePartial] (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-base/handlebars-base-min.js:6:5314)
    at Object.eval (eval at <anonymous> (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-compiler/handlebars-compiler-min.js:11:641), <anonymous>:4:17)
    at Object.o (/usr/lib/node_modules/yuidocjs/node_modules/yui/handlebars-base/handlebars-base-min.js:7:310)
error: --------------------------------------------------------------------------
error: Node.js version: v4.4.7
error: YUI version: 3.18.1
error: YUIDoc version: 0.10.2
error: Please file all tickets here: http://github.com/yui/yuidoc/issues
error: --------------------------------------------------------------------------

Note that the documentation is not correct because @extends tag is empty, but YUIDoc should only prints a warning.