gfx/video_shader_parse: accept float values for absolute scale_x/y

Many community .slangp presets — notably Mega_Bezel — write absolute
scale dimensions as floats, e.g.

   scale_type_x26 = absolute
   scale_x26      = 800.0

Before commit 1d9ed2e ("file/config_file: reject non-numeric input in
integer getters"), config_get_int silently accepted "800.0" as 800
because strtol stops at the '.', returns 800, and leaves errno == 0.
The old getter only checked errno, so it returned true with *in = 800.

After 1d9ed2e — correctly — config_get_int rejects strings with
trailing garbage and leaves *in untouched. In video_shader_parse_pass
the local iattr is initialised to 0 but scale->abs_x / abs_y are not
assigned on failure, so the absolute-scaled passes end up with a 0
dimension. The Vulkan driver then tries to build a 0×N (or 0×0)
framebuffer and crashes.

Fall back to config_get_float + roundf on the absolute branches so
the long-tail of presets using float-shaped absolute scales keeps
working without resurrecting the silent-accept behaviour in
config_file.

Hopefully fixes #18981.

Author: LibretroAdmin

gfx/video_shader_parse.c

@@ -16,6 +16,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <math.h>
 
 #ifdef HAVE_CONFIG_H
 #include "../config.h"
@@ -779,14 +780,19 @@ static bool video_shader_parse_pass(config_file_t *conf,
    if (scale->type_x == RARCH_SCALE_ABSOLUTE)
    {
       int iattr          = 0;
+      float fattr        = 0.0f;
       if (config_get_int(conf, shader_var, &iattr))
          scale->abs_x    = iattr;
+      else if (config_get_float(conf, shader_var, &fattr))
+         scale->abs_x    = (unsigned)roundf(fattr);
       else
       {
          _len = strlcpy(shader_var, "scale_x", sizeof(shader_var));
          strlcpy(shader_var + _len, formatted_num, sizeof(shader_var) - _len);
          if (config_get_int(conf, shader_var, &iattr))
             scale->abs_x = iattr;
+         else if (config_get_float(conf, shader_var, &fattr))
+            scale->abs_x = (unsigned)roundf(fattr);
       }
    }
    else
@@ -809,14 +815,19 @@ static bool video_shader_parse_pass(config_file_t *conf,
    if (scale->type_y == RARCH_SCALE_ABSOLUTE)
    {
       int iattr          = 0;
+      float fattr        = 0.0f;
       if (config_get_int(conf, shader_var, &iattr))
          scale->abs_y    = iattr;
+      else if (config_get_float(conf, shader_var, &fattr))
+         scale->abs_y    = (unsigned)roundf(fattr);
       else
       {
          _len = strlcpy(shader_var, "scale_y", sizeof(shader_var));
          strlcpy(shader_var + _len, formatted_num, sizeof(shader_var) - _len);
          if (config_get_int(conf, shader_var, &iattr))
             scale->abs_y = iattr;
+         else if (config_get_float(conf, shader_var, &fattr))
+            scale->abs_y = (unsigned)roundf(fattr);
       }
    }
    else