jplist: Fix memory leak that occurs when JSON parsing fails

Credit to OSS-Fuzz
diff --git a/fuzz/jplist-leaks/clusterfuzz-testcase-minimized-jplist_fuzzer-5069883912617984 b/fuzz/jplist-leaks/clusterfuzz-testcase-minimized-jplist_fuzzer-5069883912617984
new file mode 100644
index 0000000..a1f85f7
--- /dev/null
+++ b/fuzz/jplist-leaks/clusterfuzz-testcase-minimized-jplist_fuzzer-5069883912617984
@@ -0,0 +1 @@
+{""A}
\ No newline at end of file
diff --git a/src/jplist.c b/src/jplist.c
index 827b367..65eb528 100644
--- a/src/jplist.c
+++ b/src/jplist.c
@@ -663,6 +663,7 @@
             if (val) {
                 plist_dict_set_item(obj, key, val);
             } else {
+                free(key);
                 plist_free(obj);
                 return NULL;
             }