libobs: Default sampler sometimes unset for GL

When mixing sampling with raw loads in a shader, ending a shader with a
load would case the default sampler to become unset for OpenGL. Instead,
initialize with no sampler, and only set if there is a sampler.

libobs-opengl/gl-shaderparser.c

@@ -325,7 +325,6 @@ static inline bool gl_write_texture_call(struct gl_shader_parser *glsp,
 					 const char *call, bool sampler)
 {
 	struct cf_parser *cfp = &glsp->parser.cfp;
-	size_t sampler_id = (size_t)-1;
 
 	if (!cf_next_token(cfp))
 		return false;
@@ -335,16 +334,16 @@ static inline bool gl_write_texture_call(struct gl_shader_parser *glsp,
 	if (sampler) {
 		if (!cf_next_token(cfp))
 			return false;
-		sampler_id = sp_getsampler(glsp, cfp->cur_token);
+		const size_t sampler_id = sp_getsampler(glsp, cfp->cur_token);
 		if (sampler_id == (size_t)-1)
 			return false;
 		if (!cf_next_token(cfp))
 			return false;
 		if (!cf_token_is(cfp, ","))
 			return false;
-	}
 
-	var->gl_sampler_id = sampler_id;
+		var->gl_sampler_id = sampler_id;
+	}
 
 	dstr_cat(&glsp->gl_string, call);
 	dstr_cat(&glsp->gl_string, "(");

libobs/graphics/shader-parser.h

@@ -76,6 +76,7 @@ static inline void shader_var_init_param(struct shader_var *sv, char *type,
 	sv->name = name;
 	sv->mapping = NULL;
 	sv->array_count = 0;
+	sv->gl_sampler_id = (size_t)-1;
 	da_init(sv->default_val);
 }