Write a Python program that takes a list of numbers as input from the user, calculates the sum of all even numbers in the list, and returns the result. The program should check if the input is valid (i.e., if it's a list of numbers), and if it's not, it should return an error message. The program should also handle exceptions gracefully and return a user-friendly error message in case of any exceptions.
detectable_content:number_placeholders length_constraints:nth_paragraph_first_word detectable_format:multiple_sections change_case:capital_word_frequency keywords:letter_frequency keywords:existence keywords:forbidden_words
falling
Section
less than
less than
e
heart
falling
make sure it contains at least 1 placeholders represented by square brackets, such as [name] Write exactly 2 paragraphs each separated with two new lines answering this instruction. The first paragraph must start with "falling" Make sure to include at least 3 sections marking the beginning of each section with 'Section X' Respond with less than 4 words be in all capital letters The letter e should show up less than 5 times The response must include the keywords heart Do not include the keywords: falling