.load("") error message is confusing (empty string)

[TWiStErRob]

Glide Version/Integration library (if any): 3.5.2
Device/Android Version: S4/4.4
Issue details/Repro steps: I found this one while working on #396. The error reported when handing Glide a "" to load is extremely confusing. Somehow Glide manages to acquire a ParcelFileDescriptor for "" which obviosly can't be opened. I'm guessing there's a catch-all else branch somewhere creating a ParcelFileDescriptor when parsing as anything else fails.

The same exception is displayed through log.tag.GenericRequest.

The URL String was acquired from a utility method like this (generalized):

String findUrl(params) {
    if (isValid(params)) {
        return generateUrl(params);
    } else {
        return "";
    }
}

An obvious workaround here is to return null, but it would help to have better message for those new to Glide (and experienced users too, I was puzzled for a few minutes too).

Glide load line:

Glide.with(context)
     //.fromString() // optional, doesn't change a thing
     //.asBitmap() // only changes stacktrace slightly
     //.error(R.drawable.error) // displays correctly if provided
     .load("")
     .into(imageView)
;

Stack trace (with .asBitmap()):

04-15 13:39:50.500    1364-1364/net.twisterrob.app D/GLIDE﹕ onException(java.lang.RuntimeException: setDataSource failed: status = 0xFFFFFFEA, , Target for: android.widget.ImageView{42a97688 V.ED.... ......ID 0,0-150,150 #7f090023 app:id/image}, true)
    java.lang.RuntimeException: setDataSource failed: status = 0xFFFFFFEA
            at android.media.MediaMetadataRetriever.setDataSource(Native Method)
            at android.media.MediaMetadataRetriever.setDataSource(MediaMetadataRetriever.java:138)
            at com.bumptech.glide.load.resource.bitmap.VideoBitmapDecoder.decode(VideoBitmapDecoder.java:46)
            at com.bumptech.glide.load.resource.bitmap.FileDescriptorBitmapDecoder.decode(FileDescriptorBitmapDecoder.java:45)
            at com.bumptech.glide.load.resource.bitmap.FileDescriptorBitmapDecoder.decode(FileDescriptorBitmapDecoder.java:19)
            at com.bumptech.glide.load.resource.bitmap.ImageVideoBitmapDecoder.decode(ImageVideoBitmapDecoder.java:50)
            at com.bumptech.glide.load.resource.bitmap.ImageVideoBitmapDecoder.decode(ImageVideoBitmapDecoder.java:20)
            at com.bumptech.glide.load.engine.DecodeJob.decodeFromSourceData(DecodeJob.java:190)
            at com.bumptech.glide.load.engine.DecodeJob.decodeSource(DecodeJob.java:177)
            at com.bumptech.glide.load.engine.DecodeJob.decodeFromSource(DecodeJob.java:128)
            at com.bumptech.glide.load.engine.EngineRunnable.decodeFromSource(EngineRunnable.java:122)
            at com.bumptech.glide.load.engine.EngineRunnable.decode(EngineRunnable.java:101)
            at com.bumptech.glide.load.engine.EngineRunnable.run(EngineRunnable.java:58)
            at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)
            at com.bumptech.glide.load.engine.executor.FifoPriorityThreadPoolExecutor$DefaultThreadFactory$1.run(FifoPriorityThreadPoolExecutor.java:52)