qemu: remove useless error check

Excerpt from the virCommandAddArgBuffer() description: "Correctly
transfers memory errors or contents from buf to cmd."

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

src/qemu/qemu_command.c

@@ -6412,9 +6412,6 @@ qemuBuildNumaArgStr(const virDomainDef *def, virCommandPtr cmd)
         virBufferAdd(&buf, cpumask, -1);
         virBufferAsprintf(&buf, ",mem=%d", cellmem);
 
-        if (virBufferCheckError(&buf) < 0)
-            goto cleanup;
-
         virCommandAddArgBuffer(cmd, &buf);
     }
     ret = 0;