CRITICAL FIX: Add explicit function validation and error checking to show_scan_menu

FIXED:
- Added explicit validation that show_scan_menu() function exists before calling
- Added explicit validation that print_banner() exists before using it
- Added error output if print_banner() call fails
- Improved handling of empty available_scanners array (display '(None currently installed)')
- Added error checking to ensure functions are available before use

BEHAVIOR CHANGE:
- Menu now validates dependencies before displaying
- Better error messages if required functions are missing
- More robust handling of library sourcing failures

This should fix the issue where menu fails to display when libraries are not properly sourced.

modules/security/malware-scanner.sh

@@ -2227,20 +2227,33 @@ delete_standalone_sessions() {
 
 # Main scan menu
 show_scan_menu() {
+    # Ensure print_banner is available before calling it
+    if ! declare -f "print_banner" &>/dev/null; then
+        echo "ERROR: print_banner function not found" >&2
+        return 1
+    fi
+
     # Build reference database once for the entire menu session
     if command -v build_reference_database &>/dev/null; then
-        echo "Building system reference database..."
         build_reference_database 2>/dev/null || true
         clear
     fi
 
     while true; do
-        print_banner "Malware Scanner"
+        # Call print_banner - MUST succeed
+        print_banner "Malware Scanner" || {
+            echo "ERROR: print_banner failed" >&2
+            return 1
+        }
 
         echo "Available Scanners:"
+        if [ ${#available_scanners[@]} -eq 0 ]; then
+            echo "  (None currently installed)"
+        else
             for scanner in "${available_scanners[@]}"; do
                 echo "  • ${scanner^}"
             done
+        fi
         echo ""
 
         echo -e "${CYAN}Create New Scan:${NC}"
@@ -2590,6 +2603,13 @@ main() {
     # Don't exit if none found - menu option 9 allows installation
     detect_scanners || true
 
+    # Verify show_scan_menu exists and is callable
+    if ! declare -f "show_scan_menu" &>/dev/null; then
+        echo "ERROR: show_scan_menu function not found" >&2
+        return 1
+    fi
+
+    # Call the menu function
     show_scan_menu
 }