fix: InputRequired sen error only when data is None

Author: antoniosobrinho

src/wtforms/validators.py

@@ -316,7 +316,7 @@ def __init__(self, message=None):
         self.field_flags = {"required": True}
 
     def __call__(self, form, field):
-        if field.raw_data and field.raw_data[0]:
+        if field.raw_data is not None and field.raw_data[0] is not None:
             return
 
         if self.message is None: