Fixed a bug with meta op computeOutputDims()

include/aidge/operator/MetaOperator.hpp

@@ -74,8 +74,17 @@ public:
     }
 
     void computeOutputDims() override final {
-        // Forward dims of micro-graph
-        mGraph->forwardDims();
+        // Check first that all required inputs are available, otherwise
+        // mGraph->forwardDims() will fail!
+        bool forwarded = true;
+        for (IOIndex_t i = 0; i < nbInputs(); ++i) {
+            forwarded &= mInputs[i] ? !(getInput(i)->empty()) : false;
+        }
+
+        if (forwarded) {
+            // Forward dims of micro-graph
+            mGraph->forwardDims();
+        }
     }