Cannot implicitly convert from 'const float2' to 'float4'

I'm having a very odd error. I recently got into writing custom shaders and today began working on a simple water shader. I made some basic distortion by doing GrabPass{"_GrabTex"} at the start of the shader and using it with a normal-map based UV offset for distortion. Problem is, Unity returns an error if I go and use the result (local variable 'lol') as emission. Yet, it doesn't if I either don't set the emission property, or if I set lol to total 0. The error only occurs on Vulkan, as it seems. Why is this happening?

This works:

 half4 lol = half4(0, 0, 0, 0);
 o.Emission = lol.rgb;

This works:

 half4 lol = tex2Dproj(_GrabTex, IN.uvgrab) * (1 - c.a);
 //o.Emission = lol.rgb;

This doesn't work:

 half4 lol = tex2Dproj(_GrabTex, IN.uvgrab) * (1 - c.a);
 o.Emission = lol.rgb;

And here's the full shader:

 Shader "Custom/GargWater"
 {
     Properties
     {
         _Color ("Color", Color) = (1,1,1,1)
         _MainTex ("Albedo (RGB)", 2D) = "white" {}
         [Normal] [NoScaleOffset] _BumpMap ("Normal map (RGB)", 2D) = "bump" {}
         _BumpMult ("Normal Intensity", Range(0,2)) = 1
         _Metallic ("Metallic", Range(0,1)) = 0
         _Glossiness ("Smoothness", Range(0,1)) = 0.25
         _Distortion ("Distortion", Range(0,1)) = 0
         _Speed ("Speed", Range(0,0.1)) = 0.1
     }
     SubShader
     {
         Tags { "Queue"="Transparent" "RenderType"="Transparent" }
         GrabPass{"_GrabTex"}
         LOD 200
 
         CGPROGRAM
         // Physically based Standard lighting model, and enable shadows on all light types
         #pragma surface surf Standard alpha
 
         // Use shader model 3.0 target, to get nicer looking lighting
         #pragma target 3.0
 
         sampler2D _MainTex;
         sampler2D _BumpMap;
         sampler2D _GrabTex;
 
         struct Input
         {
             float2 uv_MainTex;
             float4 position;
             float4 uvgrab;
         };
 
         half _BumpMult;
         half _Distortion;
         half _Glossiness;
         half _Metallic;
         half _Speed;
         fixed4 _Color;
 
         void vert (appdata_base IN, out Input OUT)
         {
             OUT.position = UnityObjectToClipPos(IN.vertex);
             OUT.uv_MainTex = IN.texcoord;
             OUT.uvgrab = ComputeGrabScreenPos(OUT.position);
         }
 
         void surf (Input IN, inout SurfaceOutputStandard o)
         {
             fixed2 uv1 = IN.uv_MainTex + fixed2(_Time.y, _Time.y) * _Speed;
             fixed2 uv2 = IN.uv_MainTex + fixed2(_Time.y * 0.5, -_Time.y) * _Speed;
             half4 bump = tex2D(_BumpMap, uv1);
             half4 bump2 = tex2D(_BumpMap, uv2);
             o.Normal = UnpackScaleNormal(bump, _BumpMult) * UnpackScaleNormal(bump2, _BumpMult);
             
             half4 c = tex2D (_MainTex, uv1) * tex2D (_MainTex, uv2) * _Color;
             o.Albedo = c.rgb;
 
             o.Metallic = _Metallic;
             o.Smoothness = _Glossiness;
             o.Alpha = c.a;
             
             IN.uvgrab.x += bump.g * _Distortion * 0.1;
             IN.uvgrab.y += bump.g * _Distortion * 0.1;
             half4 lol = tex2Dproj(_GrabTex, IN.uvgrab) * (1 - c.a);
             o.Emission = lol.rgb;
         }
         ENDCG
     }
 }
 

Am I missing something here? The line the error points to is line 167, which, considering the shader ends at 75, is astoundingly useless. I'm using Unity 2019.3.15f1.