revert to avert possible thread lock
diff --git a/coders/json.c b/coders/json.c
index 6ff81e0..d61c3d3 100644
--- a/coders/json.c
+++ b/coders/json.c
@@ -787,7 +787,7 @@
           sizeof(*values));
         if (values == (IPTCInfo **) NULL)
           break;
-        value=(IPTCInfo *) AcquireQuantumMemory(1,sizeof(*value));
+        value=(IPTCInfo *) AcquireMagickMemory(sizeof(*value));
         if (value == (IPTCInfo *) NULL)
           break;
         /* Check the tag length in IPTCInfo when a new tag is added */