libyang BUGFIX incorrect character value

Probably not a problem for the compilers, but may cause issues with code
parsing tools (cppcheck).
diff --git a/src/common.c b/src/common.c
index 536b044..e96f6dd 100644
--- a/src/common.c
+++ b/src/common.c
@@ -579,7 +579,7 @@
     uint8_t expr = 0; /* 0 - position predicate; 1 - leaf-list-predicate; 2 - key-predicate */
     char quot;
 
-    assert(in[0] == '\[');
+    assert(in[0] == '[');
 
     *prefix = *id = *value = NULL;
     *prefix_len = *id_len = *value_len = 0;