prevent panic if TINI_COMMIT isn't set during build

If TINI_COMMIT isn't set, .go-autogen sets an empty value
as the "expected" commit. Attempting to truncate the value
caused a panic in that situation.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/info_unix.go

@@ -72,7 +72,9 @@ func (daemon *Daemon) fillPlatformInfo(v *types.Info, sysInfo *sysinfo.SysInfo)
 			v.InitCommit.ID = "N/A"
 		} else {
 			v.InitCommit.ID = commit
-			v.InitCommit.Expected = dockerversion.InitCommitID[0:len(commit)]
+			if len(dockerversion.InitCommitID) > len(commit) {
+				v.InitCommit.Expected = dockerversion.InitCommitID[0:len(commit)]
+			}
 		}
 	} else {
 		logrus.Warnf("failed to retrieve %s version: %s", defaultInitBinary, err)