Instead of returning an error, return an invalid duration (-1 ms)

if no duration information was available. This prevents us from
entering ERROR state, effectively rendering the player instance useless.

Change-Id: I602d2661ae8b8633360306c0ea9208fb11e2bf17
related-to-bug: 8596285
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDriver.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerDriver.cpp
index 723af09..bdafb29 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDriver.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDriver.cpp
@@ -314,11 +314,11 @@
     Mutex::Autolock autoLock(mLock);
 
     if (mDurationUs < 0) {
-        *msec = 0;
-    } else {
-        *msec = (mDurationUs + 500ll) / 1000;
+        return UNKNOWN_ERROR;
     }
 
+    *msec = (mDurationUs + 500ll) / 1000;
+
     return OK;
 }