Fix String::replace()

Fixes: espressif#4920

Author: me-no-dev

cores/esp32/WString.cpp

@@ -744,16 +744,18 @@ void String::replace(const String& find, const String& replace) {
  }
  } else if(diff < 0) {
  char *writeTo = wbuffer();
+ unsigned int l = len();
  while((foundAt = strstr(readFrom, find.buffer())) != NULL) {
  unsigned int n = foundAt - readFrom;
  memmove(writeTo, readFrom, n);
  writeTo += n;
  memmove(writeTo, replace.buffer(), replace.len());
  writeTo += replace.len();
  readFrom = foundAt + find.len();
- setLen(len() + diff);
+ l += diff;
  }
  memmove(writeTo, readFrom, strlen(readFrom)+1);
+ setLen(l);
  } else {
  unsigned int size = len(); // compute size needed for result
  while((foundAt = strstr(readFrom, find.buffer())) != NULL) {
@@ -768,7 +770,7 @@ void String::replace(const String& find, const String& replace) {
  while(index >= 0 && (index = lastIndexOf(find, index)) >= 0) {
  readFrom = wbuffer() + index + find.len();
  memmove(readFrom + diff, readFrom, len() - (readFrom - buffer()));
- int newLen = len() + diff;
+  int newLen = len() + diff;
  memmove(wbuffer() + index, replace.buffer(), replace.len());
  setLen(newLen);
  wbuffer()[newLen] = 0;