Fix for some minor issues

Thanks to Jerry x2018 for reporting those.

src/cmslut.c

@@ -817,7 +817,13 @@ cmsBool CMSEXPORT cmsStageSampleCLutFloat(cmsStage* mpe, cmsSAMPLERFLOAT Sampler
     cmsUInt32Number nInputs, nOutputs;
     cmsUInt32Number* nSamples;
     cmsFloat32Number In[MAX_INPUT_DIMENSIONS+1], Out[MAX_STAGE_CHANNELS];
-    _cmsStageCLutData* clut = (_cmsStageCLutData*) mpe->Data;
+    _cmsStageCLutData* clut;
+
+    if (mpe == NULL) return FALSE;
+
+    clut = (_cmsStageCLutData*)mpe->Data;
+
+    if (clut == NULL) return FALSE;
 
     nSamples = clut->Params ->nSamples;
     nInputs  = clut->Params ->nInputs;

src/cmsopt.c

@@ -1728,6 +1728,8 @@ cmsBool OptimizeMatrixShaper(cmsPipeline** Lut, cmsUInt32Number Intent, cmsUInt3
 
                      _cmsStageMatrixData* Data = (_cmsStageMatrixData*)cmsStageData(Matrix1);
 
+                     if (Matrix1->InputChannels != 3 || Matrix1->OutputChannels != 3) return FALSE;
+
                      // Copy the matrix to our result
                      memcpy(&res, Data->Double, sizeof(res));
 

src/cmstypes.c

@@ -1919,7 +1919,7 @@ void *Type_LUT8_Read(struct _cms_typehandler_struct* self, cmsIOHANDLER* io, cms
 
 // We only allow a specific MPE structure: Matrix plus prelin, plus clut, plus post-lin.
 static
-cmsBool  Type_LUT8_Write(struct _cms_typehandler_struct* self, cmsIOHANDLER* io, void* Ptr, cmsUInt32Number nItems)
+cmsBool Type_LUT8_Write(struct _cms_typehandler_struct* self, cmsIOHANDLER* io, void* Ptr, cmsUInt32Number nItems)
 {
     cmsUInt32Number j, nTabSize, i;
     cmsUInt8Number  val;
@@ -1932,6 +1932,12 @@ cmsBool  Type_LUT8_Write(struct _cms_typehandler_struct* self, cmsIOHANDLER* io,
 
     // Disassemble the LUT into components.
     mpe = NewLUT -> Elements;
+
+    if (mpe == NULL) {  // Should never be empty. Corrupted?
+        cmsSignalError(self->ContextID, cmsERROR_UNKNOWN_EXTENSION, "empty LUT8 is not supported");
+        return FALSE;
+    }
+
     if (mpe ->Type == cmsSigMatrixElemType) {
 
         if (mpe->InputChannels != 3 || mpe->OutputChannels != 3) return FALSE;