Fix some warnings with clang static analyzer
Only one remains (also in tbprobe.cpp), but is bougus.
As a side note, tbprobe.cpp is almost clean, only the last 3
functions probe_wdl(), root_probe() and root_probe_wdl()
are still the original ones and are quite hacky.
Somewhere in the future we will reformat also the last 3
ones. The reason why has not been done before it is because
these functions are really wrong by design and should be
rewritten entirely, not only reformatted.
No functional change.
Closes #1160