RFR: 8365609: Null pointer dereference in src/java.desktop/share/native/common/java2d/opengl/OGLBlitLoops.c OGLBlitToSurfaceViaTexture()

[Artem Semenov]

The defect has been detected and confirmed in the function OGLBlitToSurfaceViaTexture() located in the file src/java.desktop/share/native/common/java2d/opengl/OGLBlitLoops.c with static code analysis. This defect can potentially lead to a null pointer dereference.

The pointer pf is dereferenced in line 324 without checking for nullptr, although earlier in line 274 the same pointer is checked for nullptr, which indicates that it can be null.

According to [this](https://github.com/openjdk/jdk/pull/26002#issuecomment-3023050372) comment, this PR contains fixes for similar cases in other places.

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Commit messages:
 - The same issue is present in src/java.desktop/unix/native/libawt_xawt/awt/gtk3_interface.c gtk3_load()
 - The same issue is present in src/java.desktop/share/native/libsplashscreen/splashscreen_gif.c SplashDecodeGif()
 - The same issue is present in src/java.desktop/share/native/common/java2d/opengl/OGLBlitLoops.c OGLBlitSwToTexture()
 - 8365609 Null pointer dereference in src/java.desktop/share/native/common/java2d/opengl/OGLBlitLoops.c OGLBlitToSurfaceViaTexture()

Changes: https://git.openjdk.org/jdk/pull/26799/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26799&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365609
  Stats: 19 lines in 3 files changed: 9 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/26799.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26799/head:pull/26799

PR: https://git.openjdk.org/jdk/pull/26799