qsv: Error out if getting session handle failed in avfilter

Solve some issues found by an automated code scansion.
Suppress the complain "variables 'handle' is used but maybe
uninitialized".
Signed-off-by: Zhong Li <zhong.li@intel.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavfilter/qsvvpp.c

@@ -503,6 +503,11 @@ static int init_vpp_session(AVFilterContext *avctx, QSVVPPContext *s)
         }
     }
 
+    if (ret != MFX_ERR_NONE) {
+        av_log(avctx, AV_LOG_ERROR, "Error getting the session handle\n");
+        return AVERROR_UNKNOWN;
+    }
+
     /* create a "slave" session with those same properties, to be used for vpp */
     ret = MFXInit(impl, &ver, &s->session);
     if (ret != MFX_ERR_NONE) {

libavfilter/vf_deinterlace_qsv.c

@@ -201,6 +201,11 @@ static int init_out_session(AVFilterContext *ctx)
         }
     }
 
+    if (err != MFX_ERR_NONE) {
+        av_log(ctx, AV_LOG_ERROR, "Error getting the session handle\n");
+        return AVERROR_UNKNOWN;
+    }
+
     /* create a "slave" session with those same properties, to be used for
      * actual deinterlacing */
     err = MFXInit(impl, &ver, &s->session);

libavfilter/vf_scale_qsv.c

@@ -300,6 +300,11 @@ static int init_out_session(AVFilterContext *ctx)
         }
     }
 
+    if (err != MFX_ERR_NONE) {
+        av_log(ctx, AV_LOG_ERROR, "Error getting the session handle\n");
+        return AVERROR_UNKNOWN;
+    }
+
     /* create a "slave" session with those same properties, to be used for
      * actual scaling */
     err = MFXInit(impl, &ver, &s->session);