Add a check before casting $value to string when firing events

This was necessray because some types cannot be converted to string,
and it was throwing an exception when casting an Enum.

This work was done based on the PR opened by @patrocle on
#16

src/AttributeEvents.php

@@ -61,7 +61,7 @@ private function fireAttributeEvents(): void
                 || $expected === 'false' && $value === false
                 || is_numeric($expected) && Str::contains($expected, '.') && $value === (float) $expected // float
                 || is_numeric($expected) && $value === (int) $expected // int
-                || (string) $value === $expected
+                || $this->canBeCastedToString($value) && (string) $value === $expected
             ) {
                 $this->fireModelEvent($change, false);
             }
@@ -137,4 +137,16 @@ private function hasAccessor(string $attribute): bool
 
         return false;
     }
+
+    private function canBeCastedToString($value): bool
+    {
+        if ($value instanceof \UnitEnum) {
+            return false;
+        }
+
+        return is_scalar($value)
+            || is_null($value)
+            || is_array($value)
+            || is_object($value) && method_exists($value, '__toString');
+    }
 }