Allow DataAccessorIfc to throw EvaluationException.

src/main/java/com/ezylang/evalex/config/ExpressionConfiguration.java

···
 
   /** The standard set constants for EvalEx. */
   public static final Map<String, EvaluationValue> StandardConstants =
-          getStandardConstants(() -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER));
+      getStandardConstants(() -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER));
 
   /** Setting the decimal places to unlimited, will disable intermediate rounding. */
   public static final int DECIMAL_PLACES_ROUNDING_UNLIMITED = -1;

src/main/java/com/ezylang/evalex/data/DataAccessorIfc.java

···
 package com.ezylang.evalex.data;
 
 import com.ezylang.evalex.EvaluationContext;
+import com.ezylang.evalex.EvaluationException;
 
 /**
  * A data accessor is responsible for accessing data, e.g. variable values during an expression
···
    * @param variable The variable name, e.g. a variable or constant name.
    * @return The data value, or <code>null</code> if not found.
    */
-  EvaluationValue getData(String variable, EvaluationContext context);
+  EvaluationValue getData(String variable, EvaluationContext context) throws EvaluationException;
 }

src/test/java/com/ezylang/evalex/data/MapBasedDataAccessorTest.java

···
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import com.ezylang.evalex.EvaluationException;
 import java.math.BigDecimal;
 import java.util.HashMap;
 import java.util.Map;
···
 class MapBasedDataAccessorTest {
 
   @Test
-  void testSetGetData() {
+  void testSetGetData() throws EvaluationException {
     Map<String, EvaluationValue> variables = new HashMap<>();
     DataAccessorIfc dataAccessor = (variable, context) -> variables.get(variable);
 
···
   }
 
   @Test
-  void testCaseInsensitivity() {
+  void testCaseInsensitivity() throws EvaluationException {
     Map<String, EvaluationValue> variables = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
     DataAccessorIfc dataAccessor = (variable, context) -> variables.get(variable);