fix: bounding boxes of exported svg pattern pieces are now correct

[Onetchou]

Fixes #1197

[what-the-diff]

🎉 PR Summary 📝

🔹 Enhanced SVG Merging Approach: We have redefined how SVG files merge to improve the performance and ensure consistency. This reduces any potential issues and enhances the smooth running of your document. 📋

🔹 Clever Removal of '' Tags: There are times when a pesky '' tag can create problems in your merged SVG. To solve this, we've added an intelligent check that will automatically spot and remove these if they're present, keeping your document clean and efficient.👌

🔹 Slight Shift in Iterating Method: Now our iterators kick off correctly from the ground level (that's 0) which aligns perfectly with standard computing practices and provides a seamless experience. 🔄

🔹 New Superhero Functions🦸‍♂️:

• removeEmptyGroups: This hero swoops in, spotting and getting rid of any empty '' groups that might slow down the performance of the SVG.
• removeEmptyOriginPath: This function removes paths from the SVG that aren't going anywhere, preventing any possible issues and keeping everything running smoothly.
• cleanSvg: Acting as a heroic coordinator, this function summons removeEmptyGroups and removeEmptyOriginPath to tidy ups the SVG doc, ultimately promoting clean, efficient and error-free operation.✨

🔹 Code Purification: We've also spruced up addSvgFromScene, tidying up and removing unnecessary whitespaces. It's like spring cleaning for your code!💖

🔹 Header File Refresh: We've updated the svg_generator.h file with the new function declarations, ensuring everything is up-to-date and ready for action. 🚀

Every update in this PR means a more robust, efficient, and cleaner way of dealing with SVG documents. Let's continue making our project the best it can be! 🌟

[DSCaskey]

Looks good to me. I did a test export and the empty groups are no longer included causing an incorrect bounding box.