Fix misplaced nullptr checks after creating textures in W3DProjectedShadowManager

[xezon]

This change fixes misplaced tests in various functions of W3DProjectedShadowManager class.

Originally, the allocated textures would be accessed first, and then tested against null.

It needs to be the other way around, otherwise this would crash.

Additionally this change fixes some mistakes in relevant shadow assert messages.

[codecov-commenter]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (cfa005f) 2.53% compared to head (31b198c) 2.53%.

Files	Patch %	Lines
...orm/w3dengine/client/shadow/w3dprojectedshadow.cpp	0.00%	15 Missing ⚠️
...tform/w3dengine/client/shadow/w3dbuffermanager.cpp	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1103   +/-   ##
========================================
  Coverage     2.53%    2.53%           
========================================
  Files          949      949           
  Lines       110299   110299           
  Branches     18881    18881           
========================================
  Hits          2800     2800           
  Misses      107095   107095           
  Partials       404      404           

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