minor improvement to error propagation wrt MapEntrySerializer

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/ser/impl/MapEntrySerializer.java

@@ -299,7 +299,7 @@ public boolean isEmpty(SerializerProvider prov, Entry<?, ?> entry)
                 try {
                     valueSer = _findAndAddDynamic(_dynamicValueSerializers, cc, prov);
                 } catch (JsonMappingException e) { // Ugh... cannot just throw as-is, so...
-                    return false;
+                    throw new RuntimeJsonMappingException(e);
                 }
             }
         }