qemu: Fix segfault in qemuMonitorTextGetBlockInfo

If some error occurs then the cleanup code calls VIR_FREE(info)
without ensuring that info is initialized.

AUTHORS

@@ -219,6 +219,7 @@ Patches have also been contributed by:
   Laszlo Ersek         <lersek@redhat.com>
   Zeeshan Ali (Khattak) <zeeshanak@gnome.org>
   Marcelo Cerri        <mhcerri@linux.vnet.ibm.com>
+  Hendrik Schwartke    <hendrik@os-t.de>
 
   [....send patches to get your name here....]
 

src/qemu/qemu_monitor_text.c

@@ -774,7 +774,7 @@ int qemuMonitorTextGetMemoryStats(qemuMonitorPtr mon,
 int qemuMonitorTextGetBlockInfo(qemuMonitorPtr mon,
                                 virHashTablePtr table)
 {
-    struct qemuDomainDiskInfo *info;
+    struct qemuDomainDiskInfo *info = NULL;
     char *reply = NULL;
     int ret = -1;
     char *dummy;