libavfilter/vf_scale.c:174: error: Null Dereference
  pointer `desc` last assigned on line 158 could be null and is dereferenced at line 174, column 34.

libavfilter/vf_scale.c:153:1: start of procedure config_props()
151. }
152. 
153. static int config_props(AVFilterLink *outlink)
     ^
154. {
155.     AVFilterContext *ctx = outlink->src;

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

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

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

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

libavutil/pixdesc.c:1199:1: start of procedure av_pix_fmt_desc_get()
  1197. }
  1198. 
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1201:9: Taking false branch
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1201:24: Taking true branch
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1202:9: 
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1202.         return NULL;
                ^
  1203.     return &av_pix_fmt_descriptors[pix_fmt];
  1204. }

libavutil/pixdesc.c:1204:1: return from a call to av_pix_fmt_desc_get
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];
  1204. }
        ^
  1205. 
  1206. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

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

libavfilter/vf_scale.c:165:5: 
163. 
164.     var_values[VAR_PI]    = M_PI;
165.     var_values[VAR_PHI]   = M_PHI;
         ^
166.     var_values[VAR_E]     = M_E;
167.     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;

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

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

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

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

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

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

libavfilter/vf_scale.c:172:29: Condition is true
170.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
171.     var_values[VAR_DAR]   = var_values[VAR_A]  = (double) inlink->w / inlink->h;
172.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
                                 ^
173.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
174.     var_values[VAR_HSUB]  = 1 << desc->log2_chroma_w;

libavfilter/vf_scale.c:172:5: 
170.     var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
171.     var_values[VAR_DAR]   = var_values[VAR_A]  = (double) inlink->w / inlink->h;
172.     var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
         ^
173.         (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
174.     var_values[VAR_HSUB]  = 1 << desc->log2_chroma_w;

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