don't run SALV get_metadata if not displayed yet

fix #1097

src/not_cloud/zcl_excel_converter_salv_table.clas.abap

@@ -75,7 +75,16 @@ CLASS zcl_excel_converter_salv_table IMPLEMENTATION.
         ls_vari-handle    = ls_layout_key-handle.
         ls_vari-log_group = ls_layout_key-logical_group.
       ELSE.
-        io_salv->get_metadata( ) .
+        IF zcl_excel_converter_salv_model=>is_alv_displayed( io_salv ) = abap_true.
+          io_salv->get_metadata( ) .
+        ELSE.
+          " (do same as offline below)
+          cl_salv_controller_metadata=>get_variant(
+            EXPORTING
+              r_layout  = lo_layout
+            CHANGING
+              s_variant = ls_vari ).
+        ENDIF.
       ENDIF.
     ELSE.
 * If we are offline we need to build this.

src/zcl_excel_converter_salv_model.clas.abap

@@ -0,0 +1,31 @@
+CLASS zcl_excel_converter_salv_model DEFINITION
+  PUBLIC
+  INHERITING FROM cl_salv_model
+  FINAL
+  CREATE PUBLIC .
+
+  PUBLIC SECTION.
+    CLASS-METHODS is_alv_displayed
+      IMPORTING
+        io_salv       TYPE REF TO cl_salv_table
+      RETURNING
+        VALUE(result) TYPE abap_bool.
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+ENDCLASS.
+
+
+
+CLASS zcl_excel_converter_salv_model IMPLEMENTATION.
+
+  METHOD is_alv_displayed.
+    DATA: lo_model TYPE REF TO cl_salv_model.
+
+    " In 7.52 and older versions, we have a short dump with CL_SALV_TABLE->GET_METADATA if the ALV is not displayed
+    " (due to io_salv->r_controller->r_adapter not instantiated yet). That's later fixed by SAP (no short dump in 7.57).
+    " NB: r_controller is always instantiated.
+    lo_model ?= io_salv.
+    result = xsdbool( lo_model->r_controller->r_adapter IS BOUND ).
+  ENDMETHOD.
+
+ENDCLASS.

src/zcl_excel_converter_salv_model.clas.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<abapGit version="v1.0.0" serializer="LCL_OBJECT_CLAS" serializer_version="v1.0.0">
+ <asx:abap xmlns:asx="http://www.sap.com/abapxml" version="1.0">
+  <asx:values>
+   <VSEOCLASS>
+    <CLSNAME>ZCL_EXCEL_CONVERTER_SALV_MODEL</CLSNAME>
+    <LANGU>E</LANGU>
+    <DESCRIPT>SALV model utility methods</DESCRIPT>
+    <STATE>1</STATE>
+    <CLSCCINCL>X</CLSCCINCL>
+    <FIXPT>X</FIXPT>
+    <UNICODE>X</UNICODE>
+   </VSEOCLASS>
+  </asx:values>
+ </asx:abap>
+</abapGit>