cmdline: fix missing NULL at end of array of args

lvm_run needs to place NULL as the last element into argv[].
Otherwise we get:

Conditional jump or move depends on uninitialised value(s)
 _command_required_pos_matches (lvmcmdline.c:1443)
 _find_command (lvmcmdline.c:1610)
 lvm_run_command (lvmcmdline.c:2770)
 lvm2_run (lvmcmdlib.c:91)

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.172 - 
 ===============================
+  Add missing NULL to argv array when spliting cmdline arguments.
   Add display_percent helper function for printing percent values.
   Lvconvert --repair handles failing raid legs (present but marked 'D'ead).
   Do not lvdisplay --maps unset settings of cache pool.

test/api/test.c

@@ -51,6 +51,9 @@ static int lvm_split(char *str, int *argc, char **argv, int max)
 			break;
 	}
 
+	if (*argc < max)
+		argv[*argc] = NULL;
+
 	return *argc;
 }
 

tools/lvmcmdline.c

@@ -3045,6 +3045,9 @@ int lvm_split(char *str, int *argc, char **argv, int max)
 			break;
 	}
 
+	if (*argc < max)
+		argv[*argc] = NULL;
+
 	return *argc;
 }