ASessionDescription: allow open-ended NTP range.

Bug: 17435211
Change-Id: I450d512abdc4368f5180d9859f3b4e207e3b5591
diff --git a/media/libstagefright/rtsp/ASessionDescription.cpp b/media/libstagefright/rtsp/ASessionDescription.cpp
index a9b3330..98498e9 100644
--- a/media/libstagefright/rtsp/ASessionDescription.cpp
+++ b/media/libstagefright/rtsp/ASessionDescription.cpp
@@ -319,6 +319,11 @@
 
     s = end + 1;  // skip the dash.
 
+    if (*s == '\0') {
+        *npt2 = FLT_MAX;  // open ended.
+        return true;
+    }
+
     if (!strncmp("now", s, 3)) {
         return false;  // no absolute end time available
     }