Add validation before trying to read a query result (#26317)

Author: pnv1

.github/last_commit.txt

@@ -1 +1 @@
-337ad331d577c2bf3d4e92fb73a77dc37cf8fc7f
+8ca586a7fefca64794ea9ae26aed6c720d216d32

src/client/query/impl/exec_query.cpp

@@ -128,8 +128,12 @@ class TExecuteQueryIterator::TReaderImpl {
 };
 
 TAsyncExecuteQueryPart TExecuteQueryIterator::ReadNext() {
+    if (!ReaderImpl_) {
+        RaiseError("Attempt to read a stream result part on an invalid stream. ");
+    }
+
     if (ReaderImpl_->IsFinished()) {
-        RaiseError("Attempt to perform read on invalid or finished stream");
+        RaiseError("Attempt to read a stream result part on a finished stream. ");
     }
 
     return ReaderImpl_->ReadNext(ReaderImpl_);