Properly propagate errors that occur during preparation.

library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java

@@ -82,9 +82,7 @@ public class HlsSampleSource implements SampleSource, Loader.Callback {
       loader = new Loader("Loader:HLS");
     }
     continueBufferingInternal();
-    if (extractors.isEmpty()) {
-      return false;
-    }
+    if (!extractors.isEmpty()) {
       TsExtractor extractor = extractors.getFirst();
       if (extractor.isPrepared()) {
         trackCount = extractor.getTrackCount();
@@ -98,6 +96,10 @@ public class HlsSampleSource implements SampleSource, Loader.Callback {
         }
         prepared = true;
       }
+    }
+    if (!prepared && currentLoadableException != null) {
+      throw currentLoadableException;
+    }
     return prepared;
   }