input-field: Fix crash when numlock is on and numlock_color is fallback

[nasirHo]

Issue

Hyprlock crashes in updateColors() when:

• Numlock is enabled.
• colorConfig.num is a fallback value.

There is an inconsistency in condition checks when assigning and later using targetGrad:

1. When assigning targetGrad (Line 409), the condition checks both:

   • Whether numlock is enabled.
   • Whether colorConfig.num is not a fallback.

2. When using targetGrad (Line 421), the condition only checks for numlock, but does not check if numlock_color is a fallback.

   • If numlock_color is a fallback, targetGrad remains nullptr, leading to a crash.

Fix

• Updated the condition in Line 421 to match the condition used when assigning targetGrad.

[PaideiaDilemma]

Thanks!