Fix NPE in DrawableTransformation when custom transform returns null

[jayyaj12]

Description

This PR inverts the equality check in DrawableTransformation's transform method.
Instead of calling .equals() on the potentially null transformedBitmapResource, it now calls it on bitmapResourceToTransform, which is guaranteed to be non-null by the preceding null check.

Motivation and Context

If a custom Transformation implementation returns null, the current implementation throws a NullPointerException when attempting to check for equality.
By swapping the order of comparison to original.equals(transformed), we prevent this crash. This change also aligns the behavior with BitmapTransformation.

Fixes #5651

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[jayyaj12]

Branch updated and all checks passing. Ready for review when you have time. Thanks!