[PATCH] devtool: modify: fix exception

[Jamin Lin <jamin_lin@aspeedtech.com>]

Root Cause:
initial_revs is an empty dictionary and do not have "." key.

Traceback (most recent call last):
  File "scripts/devtool", line 349, in <module>
    ret = main()
  File "scripts/devtool", line 336, in main
    ret = args.func(args, config, basepath, workspace)
  File "scripts/lib/devtool/standard.py", line 922, in modify
    if not initial_revs["."]:
KeyError: '.'

Solution:
check key exists, then get its value.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
---
 scripts/lib/devtool/standard.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/lib/devtool/standard.py b/scripts/lib/devtool/standard.py
index 559fd45676..2e56cd3050 100644
--- a/scripts/lib/devtool/standard.py
+++ b/scripts/lib/devtool/standard.py
@@ -921,7 +921,7 @@ def modify(args, config, basepath, workspace):
                     if line.startswith('*'):
                         (stdout, _) = bb.process.run('git rev-parse devtool-base', cwd=srctree)
                         initial_revs["."] = stdout.rstrip()
-                if not initial_revs["."]:
+                if "." not in initial_revs:
                     # Otherwise, just grab the head revision
                     (stdout, _) = bb.process.run('git rev-parse HEAD', cwd=srctree)
                     initial_revs["."] = stdout.rstrip()
-- 
2.25.1