Quoting negative numbers when escaping the value. See #606

Author: lonnieezell

system/Database/BaseConnection.php

@@ -1319,6 +1319,10 @@ public function escape($str)
 		{
 			return ($str === false) ? 0 : 1;
 		}
+		else if (is_numeric($str) && $str < 0)
+		{
+			return "'{$str}'";
+		}
 		else if ($str === null)
 		{
 			return 'NULL';

tests/system/Database/BaseConnectionTest.php

@@ -131,5 +131,19 @@ public function testStoresConnectionTimings()
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * Ensures we don't have escaped - values...
+	 *
+	 * @see https://github.com/bcit-ci/CodeIgniter4/issues/606
+	 */
+	public function testEscapeProtectsNegativeNumbers()
+	{
+		$db = new MockConnection($this->options);
+
+		$db->initialize();
+
+		$this->assertEquals("'-100'", $db->escape(-100));
+	}
+
 
 }