libavfilter/vf_scale.c:176: error: Null Dereference
  pointer `desc` last assigned on line 159 could be null and is dereferenced at line 176, column 34.

libavfilter/vf_scale.c:154:1: start of procedure config_props()
152. }
153. 
154. static int config_props(AVFilterLink *outlink)
     ^
155. {
156.     AVFilterContext *ctx = outlink->src;

libavfilter/vf_scale.c:156:5: 
154. static int config_props(AVFilterLink *outlink)
155. {
156.     AVFilterContext *ctx = outlink->src;
         ^
157.     AVFilterLink *inlink = outlink->src->inputs[0];
158.     ScaleContext *scale = ctx->priv;

libavfilter/vf_scale.c:157:5: 
155. {
156.     AVFilterContext *ctx = outlink->src;
157.     AVFilterLink *inlink = outlink->src->inputs[0];
         ^
158.     ScaleContext *scale = ctx->priv;
159.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);

libavfilter/vf_scale.c:158:5: 
156.     AVFilterContext *ctx = outlink->src;
157.     AVFilterLink *inlink = outlink->src->inputs[0];
158.     ScaleContext *scale = ctx->priv;
         ^
159.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
160.     int64_t w, h;

libavfilter/vf_scale.c:159:5: 
157.     AVFilterLink *inlink = outlink->src->inputs[0];
158.     ScaleContext *scale = ctx->priv;
159.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
         ^
160.     int64_t w, h;
161.     double var_values[VARS_NB], res;

libavutil/pixdesc.c:1574:1: start of procedure av_pix_fmt_desc_get()
  1572. }
  1573. 
  1574. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1575. {
  1576.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1576:9: Taking false branch
  1574. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1575. {
  1576.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1577.         return NULL;
  1578.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1576:24: Taking true branch
  1574. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1575. {
  1576.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1577.         return NULL;
  1578.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1577:9: 
  1575. {
  1576.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1577.         return NULL;
                ^
  1578.     return &av_pix_fmt_descriptors[pix_fmt];
  1579. }

libavutil/pixdesc.c:1579:1: return from a call to av_pix_fmt_desc_get
  1577.         return NULL;
  1578.     return &av_pix_fmt_descriptors[pix_fmt];
  1579. }
        ^
  1580. 
  1581. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_scale.c:165:5: 
163.     int ret;
164. 
165.     var_values[VAR_PI]    = M_PI;
         ^
166.     var_values[VAR_PHI]   = M_PHI;
167.     var_values[VAR_E]     = M_E;

libavfilter/vf_scale.c:166:5: 
164. 
165.     var_values[VAR_PI]    = M_PI;
166.     var_values[VAR_PHI]   = M_PHI;
         ^
167.     var_values[VAR_E]     = M_E;
168.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;

libavfilter/vf_scale.c:167:5: 
165.     var_values[VAR_PI]    = M_PI;
166.     var_values[VAR_PHI]   = M_PHI;
167.     var_values[VAR_E]     = M_E;
         ^
168.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
169.     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;

libavfilter/vf_scale.c:168:5: 
166.     var_values[VAR_PHI]   = M_PHI;
167.     var_values[VAR_E]     = M_E;
168.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
         ^
169.     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
170.     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;

libavfilter/vf_scale.c:169:5: 
167.     var_values[VAR_E]     = M_E;
168.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
169.     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
         ^
170.     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;

libavfilter/vf_scale.c:170:5: Skipping __builtin_nanf(): method has no implementation
168.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
169.     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
170.     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
         ^
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
172.     var_values[VAR_A]     = (double) inlink->w / inlink->h;

libavfilter/vf_scale.c:171:5: Skipping __builtin_nanf(): method has no implementation
169.     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
170.     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
         ^
172.     var_values[VAR_A]     = (double) inlink->w / inlink->h;
173.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?

libavfilter/vf_scale.c:172:5: 
170.     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
172.     var_values[VAR_A]     = (double) inlink->w / inlink->h;
         ^
173.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
174.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;

libavfilter/vf_scale.c:173:29: Condition is true
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
172.     var_values[VAR_A]     = (double) inlink->w / inlink->h;
173.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
                                 ^
174.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
175.     var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];

libavfilter/vf_scale.c:173:5: 
171.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
172.     var_values[VAR_A]     = (double) inlink->w / inlink->h;
173.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
         ^
174.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
175.     var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];

libavfilter/vf_scale.c:175:5: 
173.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
174.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
175.     var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];
         ^
176.     var_values[VAR_HSUB]  = 1 << desc->log2_chroma_w;
177.     var_values[VAR_VSUB]  = 1 << desc->log2_chroma_h;

libavfilter/vf_scale.c:176:5: 
174.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
175.     var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];
176.     var_values[VAR_HSUB]  = 1 << desc->log2_chroma_w;
         ^
177.     var_values[VAR_VSUB]  = 1 << desc->log2_chroma_h;
178. 
