fix: various crashes from crash reporter

[DickSmith]

1. fix from PR #180, but with missing } added. : Fatal Exception: NSInternalInconsistencyException attempt to delete and reload the same index path`
2. fix for Fatal Exception: NSInvalidArgumentException *** -[NSPlaceholderString initWithString:]: nil argument
3. fix for Fatal Exception: NSInternalInconsistencyException negative sizes are not supported in the flow layout
4. added type safety by explicitly setting some double literals to floats for Parameter type mismatch: Values of type 'double' may not fit into the receiver type 'CGFloat'