Fix -Wswitch warning in dsql/make

Author: mrotteveel

src/dsql/make.cpp

@@ -282,6 +282,10 @@ ValueExprNode* MAKE_constant(const char* str, dsql_constant_type numeric_flag, S
 				case CONSTANT_TIMESTAMP:
 					literal->litDesc.dsc_dtype = tz ? dtype_timestamp_tz : dtype_timestamp;
 					break;
+
+				default:
+					fb_assert(false);
+					return NULL;
 			}
 
 			literal->litDesc.dsc_sub_type = 0;
@@ -312,6 +316,10 @@ ValueExprNode* MAKE_constant(const char* str, dsql_constant_type numeric_flag, S
 					else
 						*(ISC_TIMESTAMP*) literal->litDesc.dsc_address = ts.utc_timestamp;
 					break;
+
+				default:
+					fb_assert(false);
+					return NULL;
 			}
 
 			break;