libyang BUGFIX minor bug fixes found by coverity (#2386)

* src/plugins_types/union.c: coverity fix - overflowed integer argument

* src/tree_data_common.c: coveritx fix - out-of-bounds access

* src/tree_edit.h: coverity fix - out-of-bounds access

* src/tree_schema.c: coverity fix - resource leak

Author: jsc-se

src/plugins_types/union.c

@@ -350,6 +350,8 @@ union_find_type(const struct ly_ctx *ctx, struct lysc_type_union *type_u, struct
         }
         if (msg_len == -1) {
             LY_CHECK_ERR_GOTO(!errs, ret = LY_EMEM, cleanup);
+            /* for further actions in function msg_len is just 0 */
+            msg_len = 0;
         }
         for (u = 0; u < LY_ARRAY_COUNT(type_u->types); ++u) {
             if (!errs[u]) {

src/tree_data_common.c

@@ -516,6 +516,7 @@ lyd_value_store(const struct ly_ctx *ctx, struct lyd_value *val, const struct ly
 
     if (!value) {
         value = "";
+        value_len = 0;
     }
     if (incomplete) {
         *incomplete = 0;

src/tree_edit.h

@@ -148,7 +148,7 @@ void *ly_realloc(void *ptr, size_t size);
         } \
         p__ = (char *)((LY_ARRAY_COUNT_TYPE*)(p__) + 1); \
         memcpy(&(ARRAY), &p__, sizeof p__); \
-        if (ARRAY) { \
+        if ((ARRAY) && (SIZE > 0)) { \
             memset(&(ARRAY)[*((LY_ARRAY_COUNT_TYPE*)(p__) - 1)], 0, (SIZE) * sizeof *(ARRAY)); \
         } \
     }

src/tree_schema.c

@@ -788,6 +788,7 @@ lysc_path_until(const struct lysc_node *node, const struct lysc_node *parent, LY
         if (buffer) {
             strcpy(buffer, "/");
         } else {
+            free(path);
             path = strdup("/");
         }
     }