Use the top of the heap, not the bottom.

Author: Y_Less

src/amxref.cpp

@@ -160,11 +160,11 @@ const char *AMXRef::GetString(uint32_t offset) const {
 }
 
 cell AMXRef::GetStackSpaceLeft() const {
-  return GetStk() - GetHlw();
+  return GetStk() - GetHea();
 }
 
 bool AMXRef::CheckStack() const {
-  return GetStk() >= GetHlw() && GetStk() <= GetStp();
+  return GetStk() >= GetHea() && GetStk() <= GetStp();
 }
 
 void AMXRef::PushStack(cell value) {

src/amxstacktrace.cpp

@@ -185,7 +185,7 @@ AMXStackTrace GetAMXStackTrace(AMXRef amx,
                                int max_depth) {
   // Use a fake frame, hopefully without clobbering anything in silly code.
   cell stk = amx.GetStk();
-  cell hlw = amx.GetHlw();
+  cell hlw = amx.GetHea();
   if (amx.CheckStack() && amx.GetStackSpaceLeft() >= (2 * sizeof(cell))) {
     amx.SetStk(hlw + (2 * sizeof(cell)));
     amx.PushStack(cip);