metadata_scm: Avoid crashing on new svn version layouts

This avoids crashing on newer svn layouts where the entries files
don't contain three lines. If someone wants to fix this to
get the right version on newer subversion checkouts, patches
welcome but this at least stops things crashing.

[YOCTO #5363]

(From OE-Core rev: e850c53d4d8cb877a704a23f9ce02d6185ba3ffa)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/metadata_scm.bbclass

@@ -54,11 +54,13 @@ def base_get_metadata_monotone_revision(path, d):
     return monotone_revision
 
 def base_get_metadata_svn_revision(path, d):
+    # This only works with older subversion. For newer versions 
+    # this function will need to be fixed by someone interested
     revision = "<unknown>"
     try:
         with open("%s/.svn/entries" % path) as f:
             revision = f.readlines()[3].strip()
-    except IOError:
+    except IOError, IndexError:
         pass
     return revision