Clarified handling of missing drives when it shall be given up. Coverity CID 28697.

xorriso/drive_mgt.c

@@ -755,9 +755,9 @@ int Xorriso_give_up_drive(struct XorrisO *xorriso, int flag)
      Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "WARNING", 0);
      do_eject= 0;
    }
-   Xorriso_get_drive_handles(xorriso, &dinfo, &drive,
-                             "on attempt to give up drive", 2);
-   if(!in_is_out_too) {
+   ret= Xorriso_get_drive_handles(xorriso, &dinfo, &drive,
+                                  "on attempt to give up drive", 2);
+   if(ret >= 0 && !in_is_out_too) {
      if(drive!=NULL)
        isoburn_drive_release(drive, do_eject);
      if(dinfo!=NULL)

xorriso/xorriso_timestamp.h

@@ -1 +1 @@
-#define Xorriso_timestamP "2015.11.07.111034"
+#define Xorriso_timestamP "2015.11.08.110314"