[feature](Nereids) let nullable of Year, WeekOfYear and Divide be the same as implementation in BE (#12374)

These function/expression should always be nullable, so just return true in the overwrite method.
- Year
- WeekOfYear
- Divide

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Divide.java

@@ -18,6 +18,7 @@
 package org.apache.doris.nereids.trees.expressions;
 
 import org.apache.doris.analysis.ArithmeticExpr.Operator;
+import org.apache.doris.nereids.exceptions.UnboundException;
 import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
 import org.apache.doris.nereids.types.coercion.AbstractDataType;
 import org.apache.doris.nereids.types.coercion.NumericType;
@@ -50,4 +51,10 @@ public class Divide extends BinaryArithmetic {
     public AbstractDataType inputType() {
         return NumericType.INSTANCE;
     }
+
+    // Divide is implemented as a scalar function which return type is always nullable.
+    @Override
+    public boolean nullable() throws UnboundException {
+        return true;
+    }
 }

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/WeekOfYear.java

@@ -49,9 +49,10 @@ public class WeekOfYear extends BoundFunction implements UnaryExpression, Implic
         return IntegerType.INSTANCE;
     }
 
+    // Follow the return type of origin definition in the FunctionSet.
     @Override
     public boolean nullable() {
-        return child().nullable();
+        return true;
     }
 
     @Override

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/Year.java

@@ -51,9 +51,10 @@ public class Year extends BoundFunction implements UnaryExpression, ImplicitCast
         return IntegerType.INSTANCE;
     }
 
+    // Follow the return type of origin definition in the FunctionSet.
     @Override
     public boolean nullable() {
-        return child().nullable();
+        return true;
     }
 
     @Override