qemu: command: Don't bother reporting errors in smbios formatters

qemuBuildSmbiosBiosStr and qemuBuildSmbiosSystemStr return NULL if
there's nothing to format on the commandline. Reporting errors from
buffer creation doesn't make sense since it would be ignored.

src/qemu/qemu_command.c

@@ -5633,14 +5633,7 @@ qemuBuildSmbiosBiosStr(virSysinfoBIOSDefPtr def)
     if (def->release)
         virBufferAsprintf(&buf, ",release=%s", def->release);
 
-    if (virBufferCheckError(&buf) < 0)
-        goto error;
-
     return virBufferContentAndReset(&buf);
-
- error:
-    virBufferFreeAndReset(&buf);
-    return NULL;
 }
 
 
@@ -5681,14 +5674,7 @@ qemuBuildSmbiosSystemStr(virSysinfoSystemDefPtr def,
     if (def->family)
         virBufferAsprintf(&buf, ",family=%s", def->family);
 
-    if (virBufferCheckError(&buf) < 0)
-        goto error;
-
     return virBufferContentAndReset(&buf);
-
- error:
-    virBufferFreeAndReset(&buf);
-    return NULL;
 }