Revert "lavfi: always check av_expr_parse_and_eval() return value"

This reverts commit 63be97ec.

All those calls were unchecked on purpose, as explained in the comments
in the code.

libavfilter/vf_pad.c

@@ -158,10 +158,9 @@ static int config_input(AVFilterLink *inlink)
     var_values[VAR_VSUB]  = 1<<s->vsub;
 
     /* evaluate width and height */
-    if ((ret = av_expr_parse_and_eval(&res, (expr = s->w_expr),
+    av_expr_parse_and_eval(&res, (expr = s->w_expr),
                            var_names, var_values,
-                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
-        goto eval_fail;
+                           NULL, NULL, NULL, NULL, NULL, 0, ctx);
     s->w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
     if ((ret = av_expr_parse_and_eval(&res, (expr = s->h_expr),
                                       var_names, var_values,
@@ -176,10 +175,9 @@ static int config_input(AVFilterLink *inlink)
     s->w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
 
     /* evaluate x and y */
-    if ((ret = av_expr_parse_and_eval(&res, (expr = s->x_expr),
+    av_expr_parse_and_eval(&res, (expr = s->x_expr),
                            var_names, var_values,
-                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
-        goto eval_fail;
+                           NULL, NULL, NULL, NULL, NULL, 0, ctx);
     s->x = var_values[VAR_X] = res;
     if ((ret = av_expr_parse_and_eval(&res, (expr = s->y_expr),
                                       var_names, var_values,

libavfilter/vf_scale.c

@@ -177,10 +177,9 @@ static int config_props(AVFilterLink *outlink)
     var_values[VAR_VSUB]  = 1 << desc->log2_chroma_h;
 
     /* evaluate width and height */
-    if ((ret = av_expr_parse_and_eval(&res, (expr = scale->w_expr),
+    av_expr_parse_and_eval(&res, (expr = scale->w_expr),
                            var_names, var_values,
-                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
-        goto fail;
+                           NULL, NULL, NULL, NULL, NULL, 0, ctx);
     scale->w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
     if ((ret = av_expr_parse_and_eval(&res, (expr = scale->h_expr),
                                       var_names, var_values,