Handle NULL result of strdup.

The check is needed to satisfy @NonNull annotation in Java API.

BUG=26758882

Change-Id: Ie2a45a05593f2a48e23f3ca90302b78ca78a980e
diff --git a/media/mtp/MtpDeviceInfo.cpp b/media/mtp/MtpDeviceInfo.cpp
index 3e1dff7..3d5cb06 100644
--- a/media/mtp/MtpDeviceInfo.cpp
+++ b/media/mtp/MtpDeviceInfo.cpp
@@ -69,6 +69,7 @@
 
     if (!packet.getString(string)) return false;
     mVendorExtensionDesc = strdup((const char *)string);
+    if (!mVendorExtensionDesc) return false;
 
     if (!packet.getUInt16(mFunctionalMode)) return false;
     mOperations = packet.getAUInt16();
@@ -84,12 +85,16 @@
 
     if (!packet.getString(string)) return false;
     mManufacturer = strdup((const char *)string);
+    if (!mManufacturer) return false;
     if (!packet.getString(string)) return false;
     mModel = strdup((const char *)string);
+    if (!mModel) return false;
     if (!packet.getString(string)) return false;
     mVersion = strdup((const char *)string);
+    if (!mVersion) return false;
     if (!packet.getString(string)) return false;
     mSerial = strdup((const char *)string);
+    if (!mSerial) return false;
 
     return true;
 }