Avoid NegativeArraySizeException in ProxyLeakTask on short stack traces

src/main/java/com/zaxxer/hikari/pool/ProxyLeakTask.java

@@ -77,9 +77,11 @@ public void run()
       isLeaked = true;
 
       final var stackTrace = exception.getStackTrace();
-      final var trace = new StackTraceElement[stackTrace.length - 5];
+      final var trace = new StackTraceElement[Math.max(0, stackTrace.length - 5)];
 
-      System.arraycopy(stackTrace, 5, trace, 0, trace.length);
+      if (trace.length > 0) {
+         System.arraycopy(stackTrace, 5, trace, 0, trace.length);
+      }
 
       exception.setStackTrace(trace);
       LOGGER.warn("Connection leak detection triggered for {} on thread {}, stack trace follows", connectionName, threadName, exception);

src/test/java/com/zaxxer/hikari/pool/ProxyLeakTaskTest.java

@@ -0,0 +1,39 @@
+package com.zaxxer.hikari.pool;
+
+import org.junit.Test;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+
+/**
+ * Tests for {@link ProxyLeakTask}.
+ */
+public class ProxyLeakTaskTest
+{
+   @Test
+   public void runDoesNotThrowWhenStackTraceHasFewerThanFiveFrames() throws Exception
+   {
+      final Exception shortStack = new Exception();
+      shortStack.setStackTrace(new StackTraceElement[] {
+         new StackTraceElement("Foo", "a", "Foo.java", 1),
+         new StackTraceElement("Foo", "b", "Foo.java", 2)
+      });
+
+      final Constructor<ProxyLeakTask> ctor = ProxyLeakTask.class.getDeclaredConstructor();
+      ctor.setAccessible(true);
+      final ProxyLeakTask task = ctor.newInstance();
+      set(task, "exception", shortStack);
+      set(task, "threadName", "test-thread");
+      set(task, "connectionName", "test-connection");
+
+      // run() trims the first 5 (HikariCP-internal) frames; with fewer than 5 it must not throw.
+      task.run();
+   }
+
+   private static void set(final Object target, final String field, final Object value) throws Exception
+   {
+      final Field f = ProxyLeakTask.class.getDeclaredField(field);
+      f.setAccessible(true);
+      f.set(target, value);
+   }
+}