[U-Boot] [RFC/PATCHv2 1/2] Common/command: Guard strchr/strlen from NULL pointer

[Thomas Weber]

Guard strchr/strlen from being called with NULL pointer.
This line is crashing when command "env" is called without subcommand.

The cmd is NULL in this case because the calling function "do_env"
decremented the argc without checking if there are still arguments available.

Signed-off-by: Thomas Weber <weber at corscience.de>
---
Changes for v2: 
	- Use shorter way to leave function in error case.

 common/command.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/common/command.c b/common/command.c
index 0020eac..0b1a3fb 100644
--- a/common/command.c
+++ b/common/command.c
@@ -108,6 +108,8 @@ cmd_tbl_t *find_cmd_tbl (const char *cmd, cmd_tbl_t *table, int table_len)
 	int len;
 	int n_found = 0;
 
+	if (!cmd)
+		return NULL;
 	/*
 	 * Some commands allow length modifiers (like "cp.b");
 	 * compare command name only until first dot.
-- 
1.7.3.2