fix:prevent null/empty headers from being sent in function execution

[HarshMN2345]

Fix: Prevent Null/Empty Headers in Function Execution

Problem

• When creating a function execution without headers, the frontend could send a headers object like {null: ""} to the backend.
• This is not expected behavior and could cause backend errors.
• Initializing the headers array as an empty array caused runtime errors (e.g., TypeError: Cannot read properties of undefined (reading '0')) in the function execution modal UI.

Solution

• The headers array is now always initialized as [['', '']], ensuring the UI has at least one empty entry and avoiding undefined errors.
• When building the headers object for submission, only key-value pairs with a non-empty, non-whitespace key are included.
• Reactive statements which rely on the headers array now properly guard against undefined, preventing further runtime errors.

Impact

• The backend will receive only valid header key-value pairs, or an empty object if no headers are set.
• No more {null: ""} or {"": ""} headers sent to the backend.
• Eliminates runtime errors in the function execution modal.
• Users can now submit function executions safely with or without custom headers.

Closes: SER-114

After

Before

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yes