Fixed coverity issue in acl_mem.cpp: Dereference after null check

(Line 2036) Previously, if image is NULL, src_element_size is set to 0. However, there are a bunch of 'image' dereference after this check, which does not make sense since this if statement makes it seem like this function can handle a NULL image. Therefore, I replaced it with return CL_INVALID_MEM_OBJECT like some of the other functions.
(Line 6829) Except these two lines, all the other line querying about mem->block_allocation are contained in the block with a null check for mem->block_allocation. Moving the two lines with the other lines.

Author: haoxian2

src/acl_mem.cpp

@@ -2033,7 +2033,7 @@ CL_API_ENTRY cl_int CL_API_CALL clEnqueueReadImageIntelFPGA(
       return errcode_ret;
     }
   } else {
-    src_element_size = 0;
+    return CL_INVALID_MEM_OBJECT;
   }
 
   tmp_src_offset[0] = origin[0];
@@ -2773,13 +2773,17 @@ CL_API_ENTRY void *CL_API_CALL clEnqueueMapImageIntelFPGA(
         image->mem_object_type == CL_MEM_OBJECT_IMAGE1D_BUFFER) {
       if (image_slice_pitch != NULL) {
         *image_slice_pitch = 0;
+      } else {
+        BAIL_INFO(CL_INVALID_VALUE, command_queue->context,
+              "Invalid slice pitch provided");
       }
     } else if (image->mem_object_type == CL_MEM_OBJECT_IMAGE1D_ARRAY) {
       *image_slice_pitch = tmp_row_pitch;
     } else {
       *image_slice_pitch =
           image->fields.image_objs.image_desc->image_height * tmp_row_pitch;
     }
+    
     tmp_slice_pitch = *image_slice_pitch;
   }
 
@@ -6820,12 +6824,12 @@ static void acl_dump_mem_internal(cl_mem mem) {
              (mem->block_allocation->region->uses_host_system_malloc
                   ? "is malloc"
                   : "not malloc"));
+      printf("              .begin             %p\n",
+            mem->block_allocation->range.begin);
+      printf("              .end               %p\n",
+            mem->block_allocation->range.next);
     }
     printf("              .mappings          %d\n", mem->mapping_count);
-    printf("              .begin             %p\n",
-           mem->block_allocation->range.begin);
-    printf("              .end               %p\n",
-           mem->block_allocation->range.next);
     acl_print_debug_msg("              .size              %lu\n", mem->size);
     printf("              .host_ptr          %p\n",
            mem->fields.buffer_objs.host_ptr);