[PATCH] runqueue: Only attempt to print closest matching task if there is a match

[Richard Purdie <richard.purdie@linuxfoundation.org>]

This avoids backtraces some people have been seeing.

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

diff --git a/lib/bb/runqueue.py b/lib/bb/runqueue.py
index 4577236..bf2dc54 100644
--- a/lib/bb/runqueue.py
+++ b/lib/bb/runqueue.py
@@ -1224,12 +1224,11 @@ class RunQueue:
             if match is None:
                 bb.fatal("Can't find a task we're supposed to have written out? (hash: %s)?" % h)
             matches = {k : v for k, v in matches.iteritems() if h not in k}
-            latestmatch = sorted(matches.keys(), key=lambda f: matches[f])[-1]
-            prevh = __find_md5__.search(latestmatch).group(0)
-            output = bb.siggen.compare_sigfiles(latestmatch, match, recursecb)
-            bb.plain("\nTask %s:%s couldn't be used from the cache because:\n  We need hash %s, closest matching task was %s\n  " % (pn, taskname, h, prevh) + '\n  '.join(output))
-             
-
+            if len(matches):
+                latestmatch = sorted(matches.keys(), key=lambda f: matches[f])[-1]
+                prevh = __find_md5__.search(latestmatch).group(0)
+                output = bb.siggen.compare_sigfiles(latestmatch, match, recursecb)
+                bb.plain("\nTask %s:%s couldn't be used from the cache because:\n  We need hash %s, closest matching task was %s\n  " % (pn, taskname, h, prevh) + '\n  '.join(output))
 
 class RunQueueExecute: