Fix multiple bugs: missing semidefinite block handling, dual barrier function, and predictor step method

[napinoco]

Description

This pull request addresses three bugs.

1. Fix error in SDPT3soln_SEDUMIsoln.m when semidefinite blocks are absent

• Resolves runtime errors that occur when the optimization problem contains no semidefinite blocks
• Adds proper initialization of the sblk variable to handle cases where semidefinite constraints are not present

2. Fix bug in SOCP dual barrier function

• Corrects implementation error in the dual barrier function for Second-Order Cone Programming (SOCP)

3. Fix incorrect iterative solver selection in predictor step

• Corrects the predictor step implementation to use Bi-CGSTAB when LU decomposition is employed, as specified in the original research paper, instead of incorrectly using SQMR method