[#275] reputation/convert: Add nil check

In `SendIntermediateResultRequestBody`
add nil check for `trust` field.
If true, allocate new `PeerToPeerTrust`.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

v2/reputation/test/generate.go

@@ -111,10 +111,9 @@ func GenerateSendIntermediateResultRequestBody(empty bool) *reputation.SendInter
 	if !empty {
 		m.SetEpoch(123)
 		m.SetIteration(564)
+		m.SetTrust(GeneratePeerToPeerTrust(empty))
 	}
 
-	m.SetTrust(GeneratePeerToPeerTrust(empty))
-
 	return m
 }