fix host.Info() panic if /etc/debian_version is empty

The ReadLines helper function doesn't guarantee that the length of
lines is non-zero or that the lines have contents. Most callers
include a check for length but this was missing for version
fingerprinting on Debian if `/etc/debian_version` was empty, leading
to a panic.

host/host_linux.go

@@ -280,7 +280,7 @@ func PlatformInformationWithContext(ctx context.Context) (platform string, famil
 				platform = "debian"
 			}
 			contents, err := common.ReadLines(common.HostEtc("debian_version"))
-			if err == nil {
+			if err == nil && len(contents) > 0 && contents[0] != "" {
 				version = contents[0]
 			}
 		}
@@ -315,7 +315,7 @@ func PlatformInformationWithContext(ctx context.Context) (platform string, famil
 	} else if common.PathExists(common.HostEtc("alpine-release")) {
 		platform = "alpine"
 		contents, err := common.ReadLines(common.HostEtc("alpine-release"))
-		if err == nil && len(contents) > 0 {
+		if err == nil && len(contents) > 0 && contents[0] != "" {
 			version = contents[0]
 		}
 	} else if common.PathExists(common.HostEtc("os-release")) {