Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to 1e538efce498a934d52e074f095838229b9cd1af
  - Modified code to avoid null pointer exception
    
    Sonar fix
    
    Issue-ID: APPC-1550
    Change-Id: I6c6afcf13e33f06d70883a588574ed83a9e2dfdc
    Signed-off-by: Jegadeesh Babu <jegabab1@in.ibm.com>
    
diff --git a/docs/submodules/appc.git b/docs/submodules/appc.git
index 0a4c594..1e538ef 160000
--- a/docs/submodules/appc.git
+++ b/docs/submodules/appc.git
@@ -1 +1 @@
-Subproject commit 0a4c5940e9757e422adc24d84044d742563b0829
+Subproject commit 1e538efce498a934d52e074f095838229b9cd1af