input: set remaining file size to ' '/\x00 if resized
diff --git a/input.c b/input.c
index c4f6b6a..b126d32 100644
--- a/input.c
+++ b/input.c
@@ -56,11 +56,14 @@
     if (sz > run->global->mutate.maxFileSz) {
         PLOG_F("Too large size requested: %zu > maxSize: %zu", sz, run->global->mutate.maxFileSz);
     }
-    size_t old_sz = run->dynamicFileSz;
-    run->dynamicFileSz = sz;
-    if (run->global->cfg.only_printable && old_sz < sz) {
-        memset(run->dynamicFile, ' ', sz - old_sz);
+    if (sz < run->dynamicFileSz) {
+        if (run->global->cfg.only_printable) {
+            memset(&run->dynamicFile[sz], ' ', run->dynamicFileSz - sz);
+        } else {
+            memset(&run->dynamicFile[sz], '\x00', run->dynamicFileSz - sz);
+        }
     }
+    run->dynamicFileSz = sz;
 }
 
 static bool input_getDirStatsAndRewind(honggfuzz_t* hfuzz) {