meta-yadro: os-release: Fix release builds

Add a missing variable initialization that resulted
in an error during release builds

Signed-off-by: Alexander Amelkin <a.amelkin@yadro.com>
Change-Id: Id938ecb17f2a7b37816b4ff72c066ed6581f4577
diff --git a/meta-yadro/recipes-core/os-release/os-release.bbappend b/meta-yadro/recipes-core/os-release/os-release.bbappend
index ae1e955..de4f879 100644
--- a/meta-yadro/recipes-core/os-release/os-release.bbappend
+++ b/meta-yadro/recipes-core/os-release/os-release.bbappend
@@ -48,6 +48,7 @@
         product_tagged = True
         versionList.pop(0)
 
+    rcdev = ""
     version = versionList[0] if len(versionList) > 0 else ''
     if versionList[1][:2] == 'rc' or versionList[1] == 'dev': # Remove the '-rcX' and '-dev' parts
         rcdev = versionList[1]