fix thrown exception with certain calls to flyTo

[mollymerp]

Fix #4753

@mourner some cases where w0 and w1 were very similar, but w1 was zoomed out significantly from w0 were causing r() to return infinity, causing S to be initially set at NaN.

Not sure if this fix is how you'd do it but it manages to avoid the thrown Failed to Invert Matrix.

Launch Checklist

• briefly describe the changes in this PR
• write tests for all new functionality
• document any changes to public APIs
• post benchmark scores
• manually test the debug page