[GR-63826] TRegex: fix GenerateDFAImmediately option not freeing nfa matcher.

PullRequest: graal/20584

Author: djoooooe

regex/src/com.oracle.truffle.regex/src/com/oracle/truffle/regex/tregex/nodes/TRegexExecNode.java

@@ -103,6 +103,9 @@ public TRegexExecNode(RegexAST ast, TRegexExecutorNode nfaExecutor) {
         this.runnerNode = insert(nfaNode);
         if (this.regressionTestMode || !backtrackingMode && ast.getOptions().isGenerateDFAImmediately()) {
             switchToLazyDFA();
+            if (!this.regressionTestMode) {
+                nfaNode = null;
+            }
         }
         if (this.regressionTestMode) {
             regressTestBacktrackingNode = new NFARegexSearchNode(