clean dataContext.tokenContext.data buffer between each plugin call to avoid unwanted data in last parameter when it isn't full length. (#434)

src_features/signTx/logic_signTx.c

@@ -136,6 +136,7 @@ customStatus_e customProcessor(txContext_t *context) {
                 }
                 dataContext.tokenContext.fieldIndex++;
                 dataContext.tokenContext.fieldOffset = 0;
+                memset(dataContext.tokenContext.data, 0, sizeof(dataContext.tokenContext.data));
                 return CUSTOM_HANDLED;
             }